As filed with the Securities and Exchange Commission on August 2, 2005

Registration No. 333-                    

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form S-4

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

NBT Bancorp Inc.

(Exact name of registrant as specified in its charter)

52 South Broad Street

Norwich, New York 13815

(607) 337-2265

(Address, including zip code, and telephone number,

including area code, of registrant’s principal executive offices)

Daryl R. Forsythe

Chairman and Chief Executive Officer

NBT Bancorp Inc.

52 South Broad Street

Norwich, New York 13815

(607) 337-2265

(Name, address, including zip code, and telephone number,

including area code, of agent for service)

Copies to:

         Approximate date of commencement of proposed sale of the securities to the public: As soon as practicable after this Registration Statement becomes effective.

         If the securities being registered on this Form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box.    o

         If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

         If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

CALCULATION OF REGISTRATION FEE

     The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

SUBJECT TO COMPLETION, DATED AUGUST 2, 2005

[CNB LOGO]

MERGER PROPOSAL — YOUR VOTE IS IMPORTANT

      The Boards of Directors of NBT Bancorp Inc. and CNB Bancorp, Inc. have approved an agreement and plan of merger, pursuant to which CNB will merge with and into NBT. The consummation of the merger is subject to customary conditions such as shareholder and regulatory approvals.

      If the merger takes place, you will receive either 1.64 shares of NBT common stock or $38.00 in cash for each share of CNB common stock you own, unless you exercise your dissenter’s rights. You will have the opportunity to elect the form of consideration to be received for your shares (all stock, all cash, or a combination thereof), subject to allocation procedures set forth in the merger agreement which are intended to ensure that 55% of the outstanding shares of CNB common stock will be converted into shares of NBT common stock and the remaining outstanding shares of CNB common stock will be converted into cash. Therefore, your ability to receive all stock or all cash will depend on the elections of other CNB shareholders. If the price of NBT’s common stock falls below thresholds established in the merger agreement, CNB may terminate the merger agreement unless NBT decides to increase the exchange ratio.

      We expect that the merger will generally be tax-free with respect to any NBT common stock that you receive and will generally be taxable with respect to any cash that you receive. NBT’s common stock is traded on the Nasdaq Stock Market National Market Tier under the symbol “NBTB.” On                     , 2005, the closing sale price of NBT’s common stock was $          , as reported on the Nasdaq Stock Market National Market Tier. CNB’s common stock trades on the OTC Bulletin Board under the trading symbol “CNBI.OB.”

      This is a prospectus of NBT relating to its offering of up to 2,283,173 shares of NBT common stock to CNB shareholders in the proposed merger and a proxy statement of CNB. This document contains important information about NBT, CNB, the merger and the conditions that must be satisfied before the merger can occur. Please give all the information your careful attention.

      For a discussion of the risks related to the merger, see “Risk Factors” on page 13.

      Your vote is very important. The merger agreement and the merger must be approved by the holders of at least two-thirds of the outstanding shares of CNB’s common stock. Whether or not you plan to attend the special meeting of stockholders, please take the time to vote by submitting a valid proxy, by completing the enclosed proxy card and mailing it in the enclosed envelope or, if the option is available to you, by granting your proxy electronically over the Internet or by telephone. If you do not vote at all, that will, in effect, count as a vote against the merger proposal. We urge you to vote FOR the merger proposal.

      Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued in connection with the merger or determined if this proxy statement/ prospectus is accurate or complete. Any representation to the contrary is a criminal offense. The shares of NBT common stock are not savings deposit accounts or other obligations of any bank or savings association, and are not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

The date of this proxy statement/ prospectus is                     , 2005

and is first being mailed to shareholders on                     , 2005

WHERE YOU CAN FIND ADDITIONAL INFORMATION

      This proxy statement/ prospectus incorporates important business and financial information about NBT and CNB from other documents that are not included in or delivered with this proxy statement/ prospectus. This information is available to you without charge upon your written or oral request. You can obtain those documents incorporated by reference in this proxy statement/ prospectus by accessing the Securities and Exchange Commission’s website maintained at http://www.sec.gov or by requesting copies in writing or by telephone from the appropriate company at the following addresses:

NBT BANCORP INC.

52 South Broad Street

Norwich, NY 13815

Attention: Michael J. Chewens

Senior Executive Vice President and

Chief Financial Officer

(607) 337-2265

CNB BANCORP, INC.

10-24 North Main Street, P.O. Box 873

Gloversville, NY 12078

Attention: George A. Morgan

Executive Vice President and Chief Financial Officer

(518) 773-7911

      If you would like to request documents, please do so by                     , 2005 in order to receive them before the CNB special shareholder meeting. If you request any documents incorporated by reference from us, we will mail them to you promptly by first-class mail, or similar means.

      See “Where You Can Find More Information” on page 53.

CNB BANCORP, INC.

10-24 North Main Street, P.O. Box 873

Gloversville, NY 12078

(518) 773-7911

NOTICE OF SPECIAL MEETING OF SHAREHOLDERS

To Be Held on                         , 2005

       A special meeting of shareholders of CNB Bancorp, Inc. will be held on                     , 2005, at  at                     for the following purposes:

      You are entitled to notice of and to vote at the special meeting or any adjournments or postponements thereof only if you were a holder of record of CNB’s common stock at the close of business on                     , 2005.

      CNB’s Board of Directors has determined that the merger is advisable and is fair to and in the best interest of CNB’s shareholders, has unanimously approved the merger agreement and the merger, and recommends that you vote to approve the merger agreement and the merger.

      The affirmative vote of two-thirds of the shares of CNB’s common stock outstanding on                     , 2005 is required to approve the merger agreement and the merger. The required vote of CNB’s shareholders is based on the total number of shares of CNB’s common stock outstanding and not on the number of shares which are actually voted. Not returning a proxy card, not submitting your proxy by telephone or on the Internet (if that option is available to you), or not voting in person at the special meeting or abstaining from voting will have the same effect as voting AGAINST the merger agreement and the merger.

      If you hold CNB common stock on the record date, you are entitled to dissent from the merger under Section 623 of the New York Business Corporation Law. A copy of this section is attached at Appendix C to the proxy statement/ prospectus.

      It is very important that your shares be represented at the special meeting. Whether or not you plan to attend the special meeting, please complete, date and sign the enclosed proxy card and return it as soon as possible in the enclosed postage-paid envelope, or, if the option is available to you, submit your proxy by telephone or on the Internet. A shareholder who executes a proxy may revoke it at any time before it is exercised by giving written notice to the Secretary of CNB at the address set forth above, by subsequently filing another proxy or by attending the special meeting and voting in person. Do not send your stock certificate with your proxy card.

Gloversville, New York

                    , 2005

Your vote is important. Please complete, sign, date and return your proxy card.

TABLE OF CONTENTS

QUESTIONS AND ANSWERS ABOUT THE MERGER

CNB Bancorp, Inc.

10-24 North Main Street, P.O. Box 873

Gloversville, NY 12078

(518) 773-7911

SUMMARY

      The following is a summary of information located elsewhere in this document. It does not contain all of the information that is important to you. Before you vote, you should give careful consideration to all of the information contained in or incorporated by reference into this document to fully understand the merger. See “Where You Can Find More Information” on page 53. Each item in this summary refers to the page where that subject is discussed in more detail.

Material Federal Income Tax Consequences (page 36)

Those CNB shareholders who receive both NBT common stock and cash for their CNB common stock will generally recognize gain equal to the lesser of (1) the amount of cash received and (2) the excess of the “amount realized” in the transaction (i.e., the fair market value of the NBT common stock at the effective time of the merger plus the amount of cash received), over their tax basis in their CNB common stock. We expect the transaction to be tax-free to holders of CNB common stock for United States federal income tax purposes to the extent that they receive solely shares of NBT common stock pursuant to the merger. Those holders receiving solely cash for their CNB common stock will generally recognize gain or loss equal to the difference between the amount of cash received and their tax basis in their shares of CNB common stock. Different tax consequences may apply to you because of your individual circumstances or because special tax rules apply to you, for example, if you:

Tax matters are very complicated. You should consult your tax advisor for a full explanation of the tax consequences of the merger to you.

Reasons for the Merger (page 20)

The CNB Board of Directors believes that the merger presents a unique opportunity to merge with a leading community financial institution in central New York that will have significantly greater financial strength and earning power than CNB would have on its own, as well as the added scale necessary to undertake and solidify leadership positions in key business lines.

CNB Board of Directors Recommends Approval (page 20)

The CNB Board of Directors unanimously approved the merger agreement and the merger and unanimously recommends that you vote FOR approval of these matters.

In the Opinion of CNB’s Financial Advisor, the Consideration is Fair, From a Financial Point of View, to CNB’s Shareholders (page 29)

In deciding to approve the merger, CNB’s Board of Directors considered the opinion of Austin Associates, LLC, CNB’s financial advisor. The opinion concluded that the proposed consideration to be received by the holders of CNB’s common stock in the merger is fair to the shareholders from a financial point of view. This opinion is attached as Appendix B to this document. We encourage you to read this opinion carefully in order to completely understand the assumptions made, matters considered and limitation of the review made by Austin Associates, LLC, Inc. in providing this opinion.

Dissenters’ Appraisal Rights in the Merger (page 40)

Under New York law, you are entitled to dissenters’ rights of appraisal in connection with the merger. If you want to assert your appraisal rights, you must follow carefully the procedures described at Appendix C, and summarized at pages 44-46 of this document.

Differences in the Rights of Shareholders (page 46)

The rights of CNB shareholders who continue as NBT shareholders after the merger will be governed by the certificate of incorporation and bylaws of NBT rather than the certificate of incorporation and bylaws of CNB. These rights will be governed by the laws of Delaware, as the state of NBT’s incorporation, rather than the laws of New York, the state where CNB is organized.

CNB’s Officers and Directors Have Interests in the Merger Which May Be Different From Yours (pages 42-44)

At the close of business on June 30, 2005, excluding all options to purchase CNB common stock, CNB’s directors, named executive officers and their affiliates owned a total of 137,494 shares of CNB’s common stock, which was approximately 6% of the total number of shares of CNB’s common stock that were outstanding on that date. Each of CNB’s directors and named executive officers have agreed to vote his or her shares in favor of the merger agreement and merger.

Additionally, some of CNB’s directors and named executive officers may have interests in the merger as directors and employees that may be different from yours as a CNB shareholder. These interests include new agreements with certain named executive officers of CNB, the appointment of two members of the Board of Directors of CNB to the Board of Directors of NBT Bank and the appointment of each other member of the Board of Directors of CNB to the newly-formed Fulton County Advisory Board. These interests are described at pages 46-49.

Regulatory Approvals We Must Obtain to
Complete the Merger (page 26)

For the merger to take place, we need to receive the regulatory approvals of the Office of the Comptroller of the Currency, the State of New York Banking Department and the Federal Reserve Bank of New York. We have filed applications with each of these regulators.

As of the date of this document, we haven’t yet received the required approvals. We can’t be certain when or if we will obtain them.

Termination of the Merger Agreement (page 35)

The merger agreement specifies a number of situations when NBT and CNB may terminate the merger agreement, which are described on page 38. The merger agreement may be terminated at any time prior to the effective time by our mutual consent and by either of us under specified circumstances, including if the merger is not consummated by March 31, 2006, if we do not receive the necessary shareholder or regulatory approvals or if the other party breaches its agreements. CNB may terminate if NBT’s common stock price falls below thresholds set forth in the merger agreement and NBT does not increase the exchange ratio pursuant to a prescribed formula.

Information About the Special Meeting (page 15)

A special meeting of CNB shareholders will be held on                     , 2005, at                      at                     to vote on the merger agreement, the merger, and the other transactions contemplated by the merger agreement, and to address any other matters that properly come before the special meeting, or any adjournments or postponements of the meeting, including a motion to adjourn the special meeting to another time and/or place to solicit additional proxies in favor of the merger agreement and the merger or otherwise.

The Companies Involved in the Merger (page 18)

NBT Bancorp Inc.

52 South Broad Street, P.O. Box 351

Norwich, New York 13815

NBT is a registered bank holding company incorporated in Delaware and headquartered in Norwich, New York. At March 31, 2005, NBT had total consolidated assets of $4.3 billion, total deposits of $3.2 billion, and stockholders’ equity of $319.2 million, or 7.5% of total assets.

CNB Bancorp, Inc.

10-24 North Main Street, P.O. Box 873

Gloversville, NY 12078

CNB is a registered bank holding company incorporated in the State of New York and headquartered in Gloversville, New York. At March 31, 2005, CNB had total assets of $419.4 million, total deposits of $337.9 million, and stockholders’ equity of $39.4 million, or 9.4% of total assets.

MARKET PRICES AND DIVIDENDS

NBT’s Common Stock

      NBT’s common stock trades on the Nasdaq Stock Market National Market Tier under the symbol “NBTB”. The table below sets forth the range of high and low sale prices of NBT’s common stock as reported on Nasdaq, as well as cash dividends paid during the periods indicated:

      On June 13, 2005, the last trading day before the public announcement of the merger, the closing price of NBT’s common stock on the Nasdaq Stock Market National Market Tier was $23.59. On                           , 2005, the most recent practicable date before the printing of this document, the closing price of NBT’s common stock on the Nasdaq Stock Market National Market Tier was $          .

CNB’s Common Stock

      CNB’s common stock trades on the OTC Bulletin Board under the trading symbol “CNBI.OB.” and is inactively traded. The table below sets forth the range of prices of this security known to management based on records of the Company and as supplied by Ryan, Beck and Co. on a quarterly basis and the quarterly cash dividends paid during the periods indicated:

Share Information and Market Prices

      The table below presents the per share closing prices of NBT’s and CNB’s common stock as of the dates specified and the equivalent per share price for CNB common stock on (1) June 13, 2005, which was the last trading date before public announcement of the merger agreement, and (2)                           , 2005, the last practicable date before printing of this proxy statement/ prospectus. The equivalent price per share column is calculated by valuing the NBT common stock at its closing price on the relevant date, multiplying this value by the estimated 2,008,592 shares of NBT common stock being issued in the merger, and adding to this amount the estimated cash consideration of $38,078,622. This total consideration is then divided by the total number of shares of CNB common stock outstanding as of each relevant date (2,223,950 shares on June 13, 2005 and                     shares on                     , 2005). For more information about the exchange ratio and how it may be increased, see “The Merger — Merger Consideration,” and for more information about the stock prices and dividends of NBT and CNB, see “Market Prices and Dividends.”

      The market price of NBT’s common stock will fluctuate between the date of this proxy statement/ prospectus and the date on which the merger takes place. CNB’s shareholders are advised to obtain current market quotations for NBT’s common stock. No assurance can be given as to the market price of NBT’s common stock at the time of the merger, although CNB may terminate the merger agreement if NBT’s common stock price falls below certain thresholds and NBT does not increase the exchange ratio pursuant to a prescribed formula. See “The Merger — Termination and Amendment to the Merger Agreement.”

Comparative Per Share Data

      The following table shows historical information about net income per share, cash dividends per share and book value per share, and similar information reflecting the merger, which we refer to as “pro forma” information. In presenting the comparative pro forma information for the time periods shown, we assumed that we had been merged throughout those periods. The pro forma information reflects the purchase method of accounting. The pro forma information also assumes 55% of the merger consideration paid in stock and 45% in cash. NBT intends to issue trust preferred securities in aggregate principal amount of $50 million in connection with the funding of the cash portion of the merger consideration.

      The information listed as “equivalent pro forma” was obtained by multiplying the pro forma amounts by the quotient obtained by dividing the NBT Common Stock to be issued in the merger by the 1.64 share exchange ratio.

      We expect that we will incur merger and integration charges as a result of combining our companies. We also anticipate that the merger will provide the combined company with financial benefits that include reduced operating expenses. These changes and benefits are not reflected in the pro forma data. While helpful in illustrating the financial characteristics of the combined company under one set of assumptions, the pro forma information does not reflect these anticipated financial benefits and, accordingly, does not attempt to predict or suggest future results. It also does not necessarily reflect what the historical results of the combined company would have been had our companies been combined.

      The information in the following table is based on, and you should read it together with, the historical financial information that NBT and CNB have presented in prior filings with the SEC and which is incorporated into this document by reference. See “Where You Can Find More Information” on page 58 for a description of where you can find our prior filings.

SELECTED CONSOLIDATED FINANCIAL AND OTHER DATA

      The tables below present selected consolidated financial and other data for NBT and CNB as of the dates and for the periods indicated. The data for NBT is based on and should be read in conjunction with NBT’s historical consolidated financial statements and related notes which are presented in its prior filings with the SEC, and which are incorporated by reference into this document. The data for CNB is based on and should be read in conjunction with CNB’s historical consolidated financial statements and the notes thereto, which are presented in its prior filings with the SEC, which are incorporated by reference into this document. See “Where You Can Find More Information.” In the opinion of management of NBT and CNB, all adjustments necessary for a fair presentation of financial position and results of operations have been included.

Selected Consolidated Financial Data — NBT (Dollars in Thousands)

Significant Statistical Data — NBT

Selected Consolidated Financial Data and Significant Statistical Data — CNB (Dollars in Thousands)

Significant Statistical Data — CNB (Dollars in Thousands)

RISK FACTORS

      In addition to the other information included in this proxy statement/ prospectus (including the matters addressed in “Cautionary Note Regarding Forward-Looking Statements” on page 60), you should carefully consider the matters described below in determining whether to approve the merger agreement and whether to make a cash or stock election. Please also refer to the additional risk factors identified in the periodic reports and other documents of NBT and CNB incorporated by reference into this document and listed in “Where You Can Find More Information.”

The price of NBT common stock will fluctuate before and after the merger, which could increase or decrease the value of the merger consideration received by CNB shareholders receiving NBT common stock.

      On June 13, 2005, the day before the merger was announced, the closing price of a share of NBT common stock was $23.59. On                     , 2005, the most recent practicable date before the mailing of this proxy statement/ prospectus, the closing price was $          . Based on these closing prices and the 1.64 exchange ratio, the implied value of the merger consideration consisting of NBT common stock was $38.69 on June 13, 2005 and $          on                     . The price of NBT common stock may increase or decrease before and after completion of the merger. Therefore, the market value of NBT common stock received by a CNB shareholder in connection with the merger could be lower than the market value of NBT stock on June 13, 2005,                     , 2005 or the closing date of the merger, and the market value of the stock consideration could be less than the $38.00 cash consideration received by shareholders receiving the cash consideration. The market value of NBT stock received by a CNB shareholder in connection with the merger could also be higher than those trading prices, and shareholders receiving the cash consideration could receive cash worth less than the market value of the stock consideration. The market price of NBT stock fluctuates based upon general market economic conditions, NBT’s business and prospects and other factors.

NBT may fail to realize the anticipated benefits of the merger.

      The success of the merger will depend on, among other things, NBT’s ability to realize anticipated cost savings and to combine the businesses of NBT and CNB in a manner that does not materially disrupt the existing customer relationships of CNB nor result in decreased revenues resulting from any loss of customers. If NBT is not able to successfully achieve these objectives, the anticipated benefits of the merger may not be realized fully or at all or may take longer to realize than expected.

      NBT and CNB have operated and, until the completion of the merger, will continue to operate, independently. It is possible that the integration process could result in the loss of key employees, the disruption of CNB’s ongoing businesses or inconsistencies in standards, controls, procedures and policies that adversely affect the ability of NBT to maintain relationships with customers and employees or to achieve the anticipated benefits of the merger.

Shareholders may receive a form of consideration different from what they elect.

      While each CNB shareholder may elect to receive cash or NBT common stock in the merger, 55% of the CNB common stock outstanding at the completion of the merger will be converted into NBT common stock, with the remainder converted into cash. Therefore, if CNB shareholders elect more cash or stock than is available under the merger agreement, elections for the over-subscribed form of merger consideration will be prorated. As a result, if either a cash or stock election proves to be more popular among CNB shareholders, and you choose the election that is more popular, you might receive a portion of your consideration in the form of consideration that you did not elect.

If you tender shares of CNB common stock to make an election, you will not be able to sell or otherwise transfer those shares until after the merger, unless you revoke your election prior to the election deadline.

      To make a cash or stock election, you must deliver your stock certificate(s) to the exchange agent (or follow the procedures for guaranteed delivery). The deadline for doing this is 5:00 p.m. local time in Norwich, New York, on                     , 2005, the day before the special meeting of shareholders. You will not be able to sell or otherwise transfer any shares of CNB common stock that you have delivered, unless you revoke your election before the deadline by providing written notice to the exchange agent. If you do not revoke your election, you will not be able to liquidate your investment in CNB common stock for any reason until you receive cash or NBT common stock in the merger. In the time between delivery of your shares and the closing of the merger, the trading price of CNB or NBT common stock may decrease, and you might otherwise want to sell your shares of CNB common stock to gain access to cash, make other investment opportunities or reduce the potential for an additional decrease in the value of your investment.

      The date that you will receive your merger consideration depends on the completion date of the merger, which is expected to occur in the fourth quarter of 2005. The completion date of the merger might be later than expected due to unforeseen events, such as delays in obtaining regulatory approvals.

The merger agreement limits CNB’s ability to pursue alternatives to the merger.

      The merger agreement contains terms and conditions that make it difficult for CNB to sell its business to a party other than NBT. These “no shop” provisions impose restrictions on CNB that, subject to certain exceptions, limit CNB’s ability to discuss or facilitate competing third-party proposals to acquire all or a significant part of CNB.

      In addition, the board of directors of CNB has agreed that it will not recommend a competing acquisition proposal and that it will not withdraw or negatively modify the recommendation that CNB shareholders vote for the merger, subject to limited exceptions. While the board of directors could take such actions if it determined that the failure to do so would violate its fiduciary duties, doing so would entitle NBT to terminate the merger agreement and may entitle it to receive a termination fee. CNB will also be required to pay the termination fee if a competing acquisition proposal has been made known to CNB or its shareholders and the merger agreement is subsequently terminated for a variety of reasons (including because CNB shareholders fail to approve the merger or because CNB willfully breaches the merger agreement), and CNB completes, or enters into an agreement for, an alternative acquisition transaction during the 12 months after the termination of the merger agreement.

      NBT required CNB to agree to these provisions as a condition to NBT’s willingness to enter into the merger agreement. However, these provisions might discourage a third party that might have an interest in acquiring all or a significant part of CNB from considering or proposing that acquisition even if it were prepared to pay consideration with a higher per share market price than the current proposed merger consideration, and the termination fee might result in a potential competing acquirer proposing to pay a lower per share price to acquire CNB than it might otherwise have proposed to pay.

CNB’s executive officers and directors have financial interests in the merger that are different from your interest as a CNB shareholder.

      CNB executive officers negotiated the merger agreement with NBT, and the board of directors approved the agreement and is recommending that CNB shareholders vote for the agreement. In considering these facts and the other information contained in this proxy statement/ prospectus, you should be aware that CNB’s executive officers and directors have financial interests in the merger in addition to the interests that they share with you as a CNB shareholder. These interests include:

      See the discussion under the heading “Interests of CNB Directors and Executive Officers in the Merger That are Different Than Yours.”

SHAREHOLDER MEETING OF CNB BANCORP, INC.

Matters to be Considered at the Special Meeting

      We are first mailing this document to the holders of CNB’s common stock on or about                     , 2005. It is accompanied by a proxy card furnished in connection with the solicitation of proxies by the CNB Board of Directors for use at the special meeting of CNB’s shareholders on                     , 2005, at                                         , at                     . At the special meeting, the holders of CNB’s common stock will consider and vote on:

Record Date and Voting

      The CNB Board of Directors has fixed the close of business on                     , 2005 as the record date for determining the CNB shareholders entitled to receive notice of and to vote at the special meeting. Only holders of record of CNB’s common stock at the close of business on that day will be entitled to vote at the special meeting or at any adjournment or postponement of the meeting. At the close of business on                     , 2005, there were                     shares of CNB’s common stock outstanding and entitled to vote at the special meeting, held by approximately                     shareholders of record.

      Each holder of CNB’s common stock on                     , 2005 will be entitled to one vote for each share held of record on each matter that is properly submitted at the special meeting or any adjournment or postponement of the meeting. The presence, in person or by proxy, of the holders of a majority of CNB’s common stock issued and outstanding and entitled to vote at the special meeting is necessary to constitute a quorum. Abstentions and broker non-votes will be included in the calculation of the number of shares represented at the special meeting in order to determine whether a quorum has been achieved. Since approval of the merger agreement requires the affirmative vote of the holders of at least two-thirds of the shares of CNB’s common stock issued and outstanding, abstentions and broker non-votes will have the same effect as a vote against the merger agreement.

      If a quorum is not obtained, or if fewer shares of CNB’s common stock are voted in favor of the proposal for approval of the merger agreement than the number required for approval, it is expected that the special meeting will be adjourned to allow additional time for obtaining additional proxies. In that event, proxies will be voted to approve an adjournment, except for proxies as to which instructions have been given to vote against the merger agreement.

      If your proxy card is properly executed and received by CNB in time to be voted at the special meeting, the shares represented by the proxy card will be voted in accordance with the instructions marked

on the proxy card. Executed proxies with no instructions indicated on the proxy card will be voted FOR the merger agreement and the merger.

      The CNB Board of Directors is not aware of any other matters that may properly come before the special meeting. If any other matters properly come before the special meeting, the persons named in the accompanying proxy will vote the shares represented by all properly executed proxies on those matters as determined by a majority of the CNB Board of Directors.

      You are requested to complete, date and sign the accompanying proxy form and to return it promptly in the enclosed postage-paid envelope or, if the option is available to you, to grant your proxy electronically over the Internet or by telephone. Please refer to the voting instruction card used by your bank, broker or other financial institution to see if you may submit voting instructions using the Internet or telephone. The enclosed proxy card is different from the blue election form that you can use to elect to receive cash or stock in the merger. Do not return your proxy card with the election form. For information about the election form, see “The Merger — Election Procedures; Surrender of Stock Certificates”. To vote on the merger agreement, you need to complete the proxy card properly and return it in the enclosed envelope, grant your proxy electronically over the Internet or by telephone, or attend the special meeting and vote in person.

      You should not forward any stock certificates with your proxy card. If you complete an election form, you should forward your CNB stock certificates to the exchange agent with the election form. If you do not complete an election form, if the merger takes place, CNB stock certificates should be delivered in accordance with instructions that will be sent to you by NBT’s exchange agent promptly after the effective time of the merger.

Required Vote; Revocability of Proxies

      In order to approve and adopt the merger agreement, the merger of CNB and NBT and the other transactions contemplated by the merger agreement, the holders of at least two-thirds of the shares of CNB’s common stock issued and outstanding on                     , 2005, must affirmatively vote FOR the merger agreement and the merger.

      The required vote of CNB’s shareholders is based on the total number of outstanding shares of CNB’s common stock and not on the number of shares which are actually voted. Not returning a proxy card or submitting your proxy by telephone or on the Internet (if the option is available to you), not voting in person at the special meeting or abstaining from voting all will have the same effect as voting AGAINST the merger agreement and the merger.

      The directors and named executive officers of CNB beneficially owned as of June 30, 2005, a total of 137,494 shares of CNB’s common stock (excluding all options to purchase shares of CNB’s common stock), which was approximately 6% of the outstanding shares of CNB’s common stock on that date. The directors and named executive officers have agreed to vote their shares in favor of the merger agreement and the merger and against competing proposals.

      If you submit a proxy card or submit a proxy over the Internet or by telephone by following the instructions on the enclosed proxy card, attending the special meeting will not automatically revoke your proxy. However, you may revoke a proxy at any time before it is voted by:

Solicitation of Proxies

      In addition to solicitation by mail, directors, officers and employees of CNB may solicit proxies for the special meeting from shareholders personally or by telephone or telecopier without receiving additional compensation for these activities. The cost of soliciting proxies will be paid by CNB. CNB also will make arrangements with brokerage firms and other custodians, nominees and fiduciaries to send proxy materials to their principals and will reimburse those parties for their expenses in doing so. CNB has retained D.F. King & Co., Inc. to assist in soliciting proxies for the meeting and to send proxy materials to brokerage houses and other custodians, nominees and fiduciaries for transmittal to their principals, at a cost of $6,500 plus out-of-pocket expenses.

THE MERGER

      The information in this section is qualified in its entirety by reference to the full text of the merger agreement including the exhibits attached thereto, a copy of which is attached to this proxy statement/ prospectus as Exhibit A and which is incorporated by reference into this document.

The Parties

      NBT and CNB have entered into an agreement and plan of merger. Under this agreement, CNB will merge with and into NBT, and immediately thereafter City National Bank and Trust Company, which is a wholly owned subsidiary of CNB, will be merged with and into NBT Bank, N.A., a wholly owned subsidiary of NBT, with NBT and NBT Bank surviving. The consummation of the merger is subject to customary conditions such as shareholder and regulatory approvals.

      NBT is a registered bank holding company incorporated in the State of Delaware in 1986 that has elected financial holding company status, with its principal headquarters located in Norwich, New York. The Company is the parent holding company of NBT Bank, NBT Financial Services, Inc., and CNBF Capital Trust I. Through NBT Bank and NBT Financial, NBT operates as one segment focused on community banking operations. CNBF Capital Trust I was organized to raise additional Tier 1 capital. NBT’s primary business consists of providing commercial banking and financial services to its customers in its market area. The principal assets of NBT are all of the outstanding shares of common stock of its direct subsidiaries, and its principal sources of revenue are the management fees and dividends it receives from NBT Bank and NBT Financial.

      At March 31, 2005, NBT had total consolidated assets of $4.3 billion, total deposits of $3.2 billion, and stockholders’ equity of $319.2 million or 7.5% of total assets. At that date, NBT also had loans, net of $2.9 billion, which included $718 million in residential mortgage loans, $1.0 billion in commercial loans and commercial real estate mortgages, $390 million in home equity loans and $418 million in consumer loans. At March 31, 2005, nonperforming assets, which include nonaccrual loans and loans past due 90 days or more and accruing, were $17.4 million. At that date, NBT’s allowance for loan losses was $45.4 million, or 261.3% of nonperforming loans and 1.6% of total loans. For additional information about NBT that is incorporated by reference into this document, see “Incorporation of Documents by Reference.”

      NBT, as a bank holding company, is regulated by the Board of Governors of the Federal Reserve System. NBT Bank, as a national bank, is regulated by the Office of the Comptroller of the Currency and to some extent by the Federal Deposit Insurance Corporation.

      CNB is a registered bank holding company incorporated in the State of New York in 1989 that has elected financial holding company status, with its principal headquarters located in Gloversville, New York. The Company is the parent holding company of City National Bank. City National Bank is engaged in a general banking business with a range of banking and fiduciary services including checking, negotiable orders of withdrawal, savings and certificates of deposit. City National Bank also offers a wide range of loan products including commercial, real estate, and installment lending. Overdraft banking lines of credit are also provided.

      At March 31, 2005, CNB had total assets of approximately $419.4 million, total deposits of approximately $337.9 million, and stockholders’ equity of approximately $39.4 million, or 9.4% of total assets. At that date, CNB also had loans, net of $192.2 million. At March 31, 2005, CNB’s allowance for loan losses was $2.4 million, or 2000% of nonperforming loans and 1.2% of net loans. For additional information about CNB that is incorporated by reference into this document, see “Incorporation of Documents by Reference.”

      CNB, as a bank holding company, is regulated by the Board of Governors of the Federal Reserve System. City National Bank, as a national bank, is regulated by the Office of the Comptroller of the Currency and to some extent by the Federal Deposit Insurance Corporation.

Background of the Merger

      In view of local economic conditions in CNB’s markets, the planned retirement of CNB’s Chief Executive Officer in 2006 and increased competition in the financial institutions industry, beginning in the second half of 2004, CNB’s Board of Directors began to consider the steps it would need to take to enhance its community banking franchise and maximize shareholder value. The two primary alternatives that resulted from such discussions were to either remain an independent institution or engage in a strategic merger with a larger institution.

      On January 19, 2005, the Board of Directors engaged Alex Sheshunoff & Co. (“Sheshunoff”) to help it evaluate the strategic options available for CNB. At a meeting of the Board of Directors held on February 28, 2005, the directors received and considered the views of Sheshunoff. Sheshunoff’s presentation addressed trends in the banking industry, the future role of the community bank in a highly competitive environment, the relative success of others in maintaining profitable independence and various analyses of bank merger transactions. The Board of Directors carefully considered all of the information provided by Sheshunoff and, following numerous conversations during which the two primary strategic alternatives were addressed and analyzed, the CNB Board of Directors determined to investigate further the possibility of a business combination transaction with a larger financial institution.

      In March 2005, the Board of Directors decided to retain Austin Associates, LLC (“Austin Associates”) based on its substantial expertise and experience in bank merger transactions, to assist the board in seeking and evaluating merger proposals from larger financial institutions. In addition, the board authorized management to consult with CNB’s legal counsel to discuss the process of merging with a larger financial institution.

      During the latter part of March and early April 2005, Austin Associates conducted due diligence on CNB. In April and May 2005, Austin Associates held discussions with seven institutions believed by it and CNB to be potentially interested in and financially and otherwise capable of engaging in a business combination with CNB. Five of these companies expressed interest and executed confidentiality agreements with CNB and received information about CNB. During the latter part of April and early May 2005, Messrs. Smith and Morgan, together with a principal of Austin Associates, met with management of the four companies who expressed an interest in continuing discussions about a potential merger transaction.

      Following these meetings, three companies submitted preliminary, nonbinding indications of interest. At a meeting of the directors on May 10, 2005, the CNB Board of Directors reviewed with Austin Associates and CNB’s legal advisors the merger process, the results of the discussions with the three interested companies and the three preliminary, nonbinding indications of interest that had been received. In addition, Austin Associates presented profiles of, and historical financial and performance data for, each of the three companies. At the conclusion of the May 10, 2005 meeting, the directors authorized management, with the assistance of Austin Associates, to continue discussions with NBT and one of the other companies that submitted a bid and to permit each to continue their due diligence review of CNB.

      During the weeks of May 16 and 23, 2005, NBT and the other company conducted due diligence reviews of CNB. On May 23, 2005, management of NBT and management of the other company each made separate presentations to the CNB Board of Directors. Each company was instructed to submit a final, nonbinding indication of interest by June 1, 2005 along with comments on a draft merger agreement prepared by CNB’s counsel.

      On June 3, 2005, the directors again met with Austin Associates and counsel to consider the two final, nonbinding indications of interest, as well as the comments to the draft merger agreement. The Board of Directors thoroughly compared the two proposals, including the form and value of the

consideration offered, plans for integration and treatment of employees, and the ability of each to complete the transaction. Counsel reviewed with directors their fiduciary duties. At the conclusion of the meeting, the CNB Board of Directors determined that NBT’s proposed price of $38.00 per share of CNB common stock (55% in the form of NBT common stock and 45% in the form of cash) was more attractive than the other proposal and authorized management and CNB’s legal and financial advisors to seek to negotiate the terms of a definitive merger agreement with NBT.

      On June 13, 2005, the CNB Board of Directors held a special meeting to review the final terms of the proposed merger agreement. CNB’s counsel summarized for the directors the negotiations that had occurred between representatives of CNB and NBT following the last board meeting on June 3, 2005 and reviewed with the board the terms and conditions of the final merger agreement in detail, as well as other relevant aspects of the proposed transaction. Following that review, Austin Associates again analyzed the financial terms of the transaction at length, and delivered its opinion that the merger consideration was fair, from a financial point of view, to the shareholders of CNB as of that date.

      Based upon the CNB Board of Directors’ review of the definitive terms of the transactions, the opinion of Austin Associates and other relevant factors, the CNB Board of Directors, by unanimous vote of all directors, concluded that the terms and conditions of the merger agreement were fair to, and in the best interests of, CNB and its shareholders, and authorized and approved the execution of the merger agreement.

Reasons for the Merger and the Recommendation of CNB’s Board of Directors

      CNB’s Board of Directors has determined that the merger is fair to and in the best interests of CNB and its shareholders and, by the unanimous vote of all the directors of CNB present at the meeting, approved and adopted the merger agreement and the merger. ACCORDINGLY, CNB’S BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT YOU VOTE “FOR” APPROVAL OF THE MERGER AGREEMENT.

      In the course of reaching its determination, CNB’s Board of Directors consulted with its legal counsel regarding its fiduciary duties, the terms of the merger agreement and related issues; with its financial advisors regarding the financial aspects and the fairness of the transaction to the shareholders from a financial point of view; and with senior management of CNB regarding, among other things, operational matters.

      In reaching its determination to approve the merger agreement, CNB’s Board of Directors considered all factors it deemed material. The Board of Directors analyzed information with respect to the financial condition, results of operations, businesses and prospects of CNB. In this regard, CNB’s Board of Directors considered the performance trends of CNB over the past several years. The Board of Directors compared CNB’s current and anticipated future operating results to publicly available financial and other information for other similarly sized banking institutions. The board also considered the ability of CNB to grow as an independent institution, the prospects of CNB to make potential acquisitions, and its ability to further enhance shareholder value without engaging in a strategic transaction. In this regard, CNB’s Board of Directors considered the long-term as well as the short-term interests of the bank and its shareholders, including whether those interests may best be served by the continued independence of the bank.

      In reaching its decision to approve the merger agreement and the merger, the Board of Directors also considered a number of factors, including the following:

      In approving the merger, CNB’s Board of Directors was aware that as a result of the merger, CNB’s common stock will no longer be publicly traded.

      This description of the information and factors considered by CNB’s Board of Directors is not intended to be exhaustive, but is believed to include all material factors the board considered. In determining whether to approve and recommend the merger agreement, CNB’s Board of Directors did not assign any relative or specific weights to any of the foregoing factors, and individual directors may have weighed factors differently. After deliberating with respect to the merger and the merger agreement, considering, among other things, the reasons discussed above and the opinion of Austin Associates referred to above, CNB’s Board of Directors approved and adopted the merger agreement and the merger as being in the best interests of CNB and its shareholders, based on the total mix of information available to the board.

Purpose and Effects of the Merger

      The purpose of the merger is to enable NBT to acquire the assets and business of CNB through the merger of NBT and CNB. After the merger, CNB’s headquarters facility at 10-24 North Main Street in downtown Gloversville will remain open as a regional hub office and it is expected that some of CNB’s other branch banking offices will remain open and will be operated as banking offices of NBT Bank.

      NBT expects to achieve reductions in the current operating expenses of CNB upon the consolidation of CNB’s operations into NBT Bank. Upon completion of the merger, except as discussed below, the issued and outstanding shares of CNB’s common stock automatically will be converted into the merger consideration. See “Merger Consideration.”

Structure

      CNB will merge with and into NBT, and immediately thereafter City National Bank, which is a wholly owned subsidiary of CNB, will be merged with and into NBT Bank, a wholly owned subsidiary of NBT, with NBT and NBT Bank surviving. When the merger takes place, except as discussed below, each issued and outstanding share of CNB’s common stock will be converted into the right to receive cash and shares of NBT’s common stock based on the merger consideration, as described below. Cash will be paid instead of fractional shares of NBT common stock. Shares of CNB’s common stock held as treasury stock or held directly or indirectly by CNB, NBT or any of their subsidiaries, other than trust account shares and shares related to any previously contracted debt, will be canceled and shall cease to exist.

      NBT and CNB expect that the merger will take place in the fourth quarter of 2005, or as soon as possible after we receive all required regulatory and shareholder approvals and all regulatory waiting periods expire. If the merger does not take place by March 31, 2006, the merger agreement may be terminated by either party (excluding any breaching party) unless both parties agree to extend it.

Merger Consideration

      The merger agreement provides that CNB shareholders will have the right, with respect to each of their shares of CNB common stock, to elect to receive, subject to proration as described below, either (i) 1.64 shares of NBT’s common stock, or (ii) $38.00 in cash. However, if the price of NBT’s common stock falls below thresholds set forth in the merger agreement, CNB may terminate the merger agreement unless NBT decides to increase the exchange ratio, which would result in NBT issuing more shares of its common stock to complete the merger. See “Termination and Amendment of the Merger Agreement.”

      Non-Electing Shares. CNB shareholders who make no election to receive cash or NBT common stock in the merger, and CNB shareholders who do not make a valid election, will be deemed not to have made an election. Shareholders not making an election may be paid in cash, NBT common stock or a mix of cash and shares of NBT common stock depending on, and after giving effect to, the number of valid cash elections and stock elections that have been made by other CNB shareholders using the proration adjustments described below.

      Election Limitations. The number of shares of CNB common stock that will be converted into NBT common stock in the merger is fixed at 55% of the total CNB common shares outstanding immediately before completion of the merger. The remainder, or 45%, of the CNB common shares will be converted into the cash consideration. Therefore, the cash and stock elections are subject to proration to preserve this requirement regarding the number of shares of NBT common stock to be issued and the cash to be paid in the merger. As a result, if you elect to receive only cash or only stock, you may nevertheless receive a mix of cash and stock.

      Proration if Too Much Stock is Elected. If CNB shareholders elect to receive more NBT common stock than NBT has agreed to issue in the merger, then CNB shareholders who elected to receive cash or who have made no election will receive cash for each share of CNB common stock they own. All CNB shareholders who elected to receive NBT common stock will receive a pro rata portion of the available NBT shares plus the cash consideration for those shares not converted into NBT common stock.

      Proration if Too Much Cash is Elected. If CNB shareholders elect to receive fewer shares of NBT common stock than NBT has agreed to issue in the merger, then all CNB shareholders who elected to receive NBT common stock will receive NBT common stock and those shareholders who have elected cash or have made no election will be treated in the following manner:

      No guarantee can be made that you will receive solely stock or solely cash, if you so elect. As a result of the allocation procedures and other limitations outlined in this document and in the merger agreement, you may receive NBT common stock or cash in amounts that vary from the amounts you elect to receive.

      Certificates for fractions of shares of NBT’s common stock will not be issued. Instead of a fractional share of NBT’s common stock, a CNB shareholder will be entitled to receive an amount of cash equal to the fraction of a share of NBT’s common stock to which the shareholder would otherwise be entitled multiplied by the average of the daily closing prices per share for NBT’s common stock for the five consecutive trading days immediately preceding, but not including, the closing date of the merger.

      The conversion of CNB’s common stock into merger consideration will occur automatically upon completion of the merger. Under the merger agreement, after the effective time of the merger, NBT will cause its exchange agent to pay the “purchase price” to each CNB shareholder who surrenders the appropriate documents to the exchange agent. In this document, we use the term “purchase price” to refer to the (i) shares (if any) of NBT’s common stock, (ii) cash (if any) and (iii) any cash to be paid instead of a fraction of a share of NBT’s common stock, payable to each holder of CNB’s common stock.

Election Procedures; Surrender of Stock Certificates

      An election form is being sent together with this proxy statement/ prospectus. The election form entitles the record holder of CNB common stock to indicate a preference to receive either (a) $38.00 in cash, without interest, or (b) 1.64 shares of NBT common stock. If no election is made, then such holder shall receive cash, stock or a combination of cash and stock in the merger as outlined above.

      To make an effective election, a record shareholder must submit a properly completed election form to                     , which will be acting as the exchange agent, on or before 5:00 p.m. local time in Norwich,

New York, on                     , 2005. An election form will be deemed properly completed only if accompanied by stock certificates representing all shares of CNB common stock covered by the election form (or an appropriate guarantee of delivery). You may change your election at any time prior to the election deadline by written notice accompanied by a properly completed and signed, revised election form received by the exchange agent prior to the election deadline. You may revoke your election by written notice received by the exchange agent prior to the election deadline or by withdrawal of your stock certificates prior to the election deadline. All elections will be revoked automatically if the merger agreement is terminated.

      Shareholders will not be entitled to revoke or change their elections following the election deadline. As a result, shareholders who have made elections will be unable to sell their shares of CNB common stock during the interval between the election deadline and the date of completion of the merger.

      If stock certificates for CNB common stock are not immediately available or time will not permit the election form and other required documents to reach the exchange agent prior to the election deadline, CNB shares may be properly exchanged provided that:

      CNB shareholders who do not submit a properly completed election form or revoke their election form prior to the election deadline will have their shares of CNB common stock designated as non-election shares and will receive cash, stock or a combination of stock and cash as outlined above. CNB stock certificates represented by elections that have been revoked or not fulfilled will be returned without charge.

      CNB shareholders who hold their shares of common stock in “street name” through a bank, broker or other financial institution, and who wish to make an election, should seek instructions from the financial institution holding their shares concerning how to make the election.

      NBT will deposit with the exchange agent the certificates representing NBT’s common stock and cash to be issued to CNB shareholders in exchange for CNB’s common stock. As soon as practicable after the completion of the merger, the exchange agent will mail to CNB shareholders who do not submit election forms a letter of transmittal, together with instructions for the exchange of their CNB stock certificates for the merger consideration. Upon surrendering his or her certificate(s) representing shares of CNB’s common stock, together with the signed letter of transmittal, the CNB shareholder shall be entitled to receive, as applicable (i) certificate(s) representing a number of whole shares of NBT’s common stock determined in accordance with the exchange ratio, (ii) a check representing the amount of cash to which such holder shall have become entitled to, and (iii) a check representing the amount of cash in lieu of fractional shares. You will not be paid dividends or other distributions declared after the merger with respect to any NBT common stock into which your shares have been converted until you surrender your CNB stock certificates for exchange. No interest will be paid or accrue to CNB shareholders on the cash consideration, cash instead of fractional shares or unpaid dividends and distributions, if any. After the effective time of the merger, there will be no further transfers of the CNB common stock. CNB stock certificates presented for transfer after the completion of the merger will be canceled and exchanged for the merger consideration.

      If your stock certificates have been lost, stolen or destroyed, you will have to prove your ownership of these certificates, certify that they were lost, stolen or destroyed and post a bond in such amount as NBT may reasonably direct before you receive any consideration for your shares. Upon request, NBT will send you instructions on how to provide evidence of ownership.

      If any certificate representing shares of NBT’s common stock is to be issued in a name other than that in which the certificate for shares surrendered in exchange is registered, or cash is to be paid to a person other than the registered holder, it will be a condition of issuance or payment that the certificate so surrendered be properly endorsed or otherwise be in proper form for transfer and that the person requesting the exchange either:

      Any portion of the purchase price made available to the exchange agent that remains unclaimed by CNB shareholders for six months after the effective time of the merger will be returned to NBT. Any CNB shareholder who has not exchanged shares of CNB’s common stock for the purchase price in accordance with the merger agreement before that time may look only to NBT for payment of the purchase price for these shares and any unpaid dividends or distributions after that time. Nonetheless, NBT, CNB, the exchange agent or any other person will not be liable to any CNB shareholder for any amount properly delivered to a public official under applicable abandoned property, escheat or similar laws.

Treatment of CNB Stock Options

      CNB Stock Option Plan. In accordance with the CNB Stock Option Plan, in connection with the merger agreement, each outstanding option to purchase shares of CNB common stock under the CNB Stock Option Plan outstanding and unexercised immediately prior thereto will become vested, to the extent not already vested, and immediately exercisable. Each holder of an option to purchase shares of CNB common stock under the CNB Stock Option Plan will be given the opportunity to elect to receive at the effective time of the merger a cash payment equal to $38.00 less the exercise price per share of the stock option, multiplied by the number of shares of CNB common stock subject to the stock option, less any required tax withholding. Upon consummation of the merger, all outstanding and unexercised options that have not otherwise been cashed-out pursuant to the foregoing election will terminate. CNB will provide each holder of an option to purchase shares of CNB common stock under the CNB Stock Option Plan written notice informing each such holder of their rights to exercise, the cash election, and the termination of any outstanding and unexercised options as of the effective time.

      CNB Long Term Incentive Compensation Plan and Adirondack Financial Services Bancorp, Inc. 1998 Stock Option and Incentive Plan. Upon completion of the merger, all outstanding stock options under the CNB Long Term Incentive Compensation Plan and the Adirondack Financial Services Bancorp, Inc. 1998 Stock Option and Incentive Plan, whether or not such options are exercisable or vested, will be cancelled and converted into the right to receive, a cash payment equal to $38.00 less the exercise price per share of the stock option, multiplied by the number of shares of CNB common stock subject to the stock option, less any required tax withholding. CNB will provide each holder of an option to purchase shares of CNB common stock under these plans a written notice informing each holder of their right to receive the cash payment and of the termination of any outstanding and unexercised options as of the effective time.

      Upon completion of the merger, each CNB stock option that is an “incentive option” under Section 422 of the Internal Revenue Code of 1986, as amended, and outstanding and unexercised immediately thereto, whether or not exercisable or vested, will become vested and will be converted into

an option to purchase shares of NBT common stock in an amount and at an exercise price determined on the following basis:

      The adjustment will be made in a manner consistent with Section 424 of the Internal Revenue Code of 1986, as amended.

Regulatory Approvals

      For the mergers of NBT and CNB and of NBT Bank and City National Bank to take place, we must receive approvals of the Office of the Comptroller of the Currency (the “OCC”), the Federal Reserve Bank of New York (the “FRB”), and the New York State Banking Department (“NYSBD”), or waivers of the applicable filing requirements. In this section, we refer to these approvals as the “required regulatory approvals”. NBT and CNB have agreed to cooperate to obtain the required regulatory approvals.

      NBT Bank has filed with the OCC an application for approval of the merger of NBT Bank and City National Bank. We refer to that merger in this section as the “bank merger”. The bank merger is subject to the approval of the OCC under the National Bank Consolidation and Merger Act, the Bank Merger Act provisions of the Federal Deposit Insurance Act and related OCC regulations. These approvals require consideration by the OCC of various factors, including assessments of the competitive effect of the contemplated transaction, the managerial and financial resources and future prospects of the resulting institution, the effectiveness of the institutions involved in combating money laundering, and the effect of the contemplated transaction on the convenience and needs of the communities to be served. The Community Reinvestment Act of 1977, commonly referred to as the “CRA”, also requires that the OCC, in deciding whether to approve the bank merger, assess the records of performance of NBT Bank and City National Bank in meeting the credit needs of the communities they serve, including low and moderate income neighborhoods. As part of the review process, it is not unusual for the OCC to receive protests and other adverse comments from community groups and others. NBT Bank currently has an “Outstanding” CRA rating from the OCC. City National Bank currently has a “Satisfactory” CRA rating from the OCC. The OCC regulations require publication of notice and an opportunity for public comment concerning the applications filed in connection with the bank merger, and authorize the OCC to hold informal and formal meetings in connection with the applications if the OCC, after reviewing the applications or other materials, determines it desirable to do so or receives a request for an informal meeting. Any meeting or comments provided by third parties could prolong the period during which the merger is subject to review by the OCC. The bank merger may not take place for a period of either 15 or 30 days following OCC approval, during which time the Department of Justice has authority to challenge the merger on antitrust grounds. The OCC will determine the precise length of the period in consultation with the Department of Justice. The commencement of an antitrust action would stay the effectiveness of any approval granted by the OCC unless a court specifically orders otherwise. If the Department of Justice does not start a legal action during the waiting period, it may not challenge the transaction afterward, except in an action under Section 2 of the Sherman Antitrust Act.

      NBT has filed with the FRB an application under the Bank Holding Act of 1956, as amended, for approval of the merger of NBT and CNB. In processing this application, the FRB will evaluate NBT under the same standards set forth above for the Bank Merger Act filing with the OCC. This filing will also be subject to a Department of Justice antitrust review period.

      NBT also has filed an application with the NYSBD to form a bank holding company for purposes of the New York Banking Law. The application is subject to NYSBD review and approval under Section 142 of the New York Banking Law. The application will be acted upon by the NYSBD within 120 days of its submission. In determining whether to approve the application, the NYSBD is required to consider whether (i) approval is consistent with the declaration of policy contained in Section 10 of the New York Banking Law, (ii) the size of the proposed holding company would be consistent with adequate or sound banking and the preservation thereof, or would result in a concentration of assets beyond limits consistent with effective competition, (iii) the formation of the bank holding company may result in such a lessening of competition as to be injurious to the interest of the public or tend toward monopoly, and (iv) the proposed formation is consistent with the public interest and the needs and convenience thereof. As part of this analysis, the NYSBD will consider the CRA ratings of the depository institutions involved and their records of meeting the credit needs of the entire community, including low- and moderate-income neighborhoods, as well as any public comments received on the proposal.

      NBT and CNB are not aware of any other material governmental approvals that are required for the holding company and bank mergers to take place that are not described above. If any other approval or action is required, we expect that we would seek the approval or take the necessary action.

      The merger cannot take place without the required regulatory approvals or waivers, which we have not yet received. There is no assurance that we will receive these approvals or waivers, or if we do, when we will receive them or that they will not contain a non-customary condition that materially alters the anticipated benefits and effects of the bank merger. Also, there is no assurance that the Department of Justice will not challenge the merger on antitrust grounds following OCC or FRB approval, or, if a challenge is made, what the result of a challenge would be.

Conditions to the Merger

      Under the merger agreement, NBT and CNB are not obligated to complete the merger unless the following conditions are satisfied:

      Stockholder approval and regulatory approvals may not be legally waived.

Conduct of Business Pending the Merger

      The merger agreement contains various restrictions on the operations of CNB before the effective time of the merger. In general, the merger agreement obligates CNB to continue to carry on its businesses in the ordinary course consistent with past practices and with prudent banking practices, with specific limitations on the lending activities and other operations of CNB.

      In addition, CNB has agreed that, except as expressly contemplated by the merger agreement or specified in a schedule to the merger agreement, without the prior written consent of NBT, it will not, among other things:

      In addition to the covenants described under “Conduct of Business Pending the Merger,” the merger agreement contains various other customary covenants, including, among other things, access to information, each party’s efforts to cause its representations and warranties to be true and correct on the closing date; and each party’s agreement to use its reasonable best efforts to cause the merger to qualify as a tax-free reorganization.

      Until the merger is completed or the merger agreement is terminated, CNB has agreed that it, its subsidiaries, its officers and its directors will not, among other things:

      CNB may, however, furnish information regarding CNB to, or enter into and engage in discussion with, any person or entity in response to an unsolicited acquisition proposal by the person or entity relating to an acquisition proposal if:

Representations and Warranties

      The merger agreement contains a number of customary representations and warranties by NBT and CNB regarding aspects of their respective businesses, financial condition, structure and other facts pertinent to the merger that are customary for a transaction of this kind. They include, among other things:

and, with respect to CNB only:

      All representations, warranties and covenants of the parties, other than the covenants in specified sections which relate to continuing matters, terminate upon the merger.

Fairness Opinion of Austin Associates, LLC

      CNB retained Austin Associates on March 14, 2005 to provide financial advisory services in connection with the potential sale of CNB. CNB selected Austin Associates as its financial adviser on the basis of Austin Associates’ historical relationship with CNB, and Austin Associates’ experience and expertise in representing community banks in similar transactions.

      On June 13, 2005, Austin Associates delivered to CNB’s board, in conjunction with its meeting held to consider the merger, its opinion to the effect that the terms of the merger agreement are fair, from a financial point of view, to CNB and its shareholders.

      You should consider the following when reading the discussion of Austin Associates’ opinion in this document:

      The preparation of a financial fairness opinion involves various determinations as to the most appropriate methods of financial analysis and the application of those methods to the particular circumstances. It is, therefore, not readily susceptible to partial analysis or summary description. In connection with rendering its opinion, Austin Associates performed a variety of financial analyses. Austin Associates believes that its analyses and the facts considered in its analyses, without considering all other factors and analyses could create an incomplete or inaccurate view of the analyses and the process underlying the rendering of Austin Associates’ opinion. No limitations were imposed by CNB’s board or its management upon Austin Associates with respect to the investigations made or the procedures followed by Austin Associates in rendering its opinion.

      In performing its analyses, Austin Associates made numerous assumptions with respect to industry performance, business and economic conditions, and other matters, many of which are beyond the control of NBT and CNB and may not be realized. Any estimates contained in Austin Associates’ analyses are not necessarily predictive of future results or values, and may be significantly more or less favorable than the estimates. Estimates of values of companies do not purport to be appraisals or necessarily reflect the prices at which the companies or their securities may actually be sold. Except as described below, none of the analyses performed by Austin Associates was assigned a greater significance by Austin Associates than any other. The relative importance or weight given to these analyses is not affected by the order of the analyses or the corresponding results. The summaries of financial analyses include information presented in tabular format. The tables should be read together with the text of those summaries.

      Austin Associates has relied, without independent verification, upon the accuracy and completeness of the information it reviewed for the purpose of rendering its opinion. Austin Associates did not undertake any independent evaluation or appraisal of the assets and liabilities of NBT or CNB, nor was it furnished with any appraisals. Austin Associates has not reviewed any individual credit files of NBT or CNB, and has assumed that NBT’s and CNB’s allowances are, in the aggregate, adequate to cover losses. Austin Associates’ opinion is based on economic, market and other conditions existing on the date of its opinion.

      In rendering its opinion, Austin Associates made the following assumptions:

      In connection with its opinion, Austin Associates reviewed:

      In addition, Austin Associates:

      The following is a summary of all material analyses performed by Austin Associates in connection with its opinion provided to the CNB board of directors as of June 13, 2005. The summary does not purport to be a complete description of the analyses performed by Austin Associates.

      The Process for Soliciting Indications of Interest. After analysis and discussions with CNB, Austin Associates contacted select banking organizations based on quality and level of overall financial performance, asset size, stock trading activity and geographic scope of operations. Seven organizations were contacted, of which five organizations executed confidentiality agreements and received a confidential information memorandum that provided detailed information regarding the business and operations of CNB. Each organization was requested to submit a specific proposal to acquire CNB. Three written offers were received, and following due diligence by two of the parties, the financial terms of the NBT proposal were deemed to be superior to the other offers received.

      Summary of Financial Terms of Agreement. Austin Associates reviewed the financial terms of the proposed transaction, including the form of consideration, the exchange ratio for the stock portion of the purchase price, and the resulting price per share of CNB common stock pursuant to the proposed merger. Under the terms of the merger agreement, each outstanding share of CNB will elect to receive either $38.00 per share in cash or 1.64 shares of NBT common stock. The agreement requires that 55 percent of CNB shares will receive NBT common stock and 45 percent of CNB’s shares will receive cash. The agreement also provides for the exchange of CNB incentive stock options for options to purchase NBT common stock and for the payment of cash for all nonqualified options of CNB for the difference between $38.00 per share and the exercise price of each nonqualified option.

      Based on 2,221,520 common shares of CNB and stock options to acquire 309,885 common shares of CNB with a weighted average exercise price of $26.41, the negotiated value of the transaction was approximately $88.0 million as of June 12, 2005. Austin Associates calculated that the value of $88.0 million represented:

      Industry Comparative Analysis. In connection with rendering its opinion, Austin Associates compared selected results of CNB’s operating performance to those of 17 New York-based community banking organizations that are publicly traded having total assets between $250 million and $1 billion. Austin Associates considered this group of financial institutions comparable to CNB on the basis of asset size and geographic location. Austin Associates noted the following selected financial measures for the New York-based banks as of March 31, 2005 as compared to CNB:

LTM = last 12 months

      This comparison indicated that CNB approximates that of the peer group in overall profitability. CNB’s level of capital as measured by the leverage ratio is above the New York peer median. Asset quality measure compares favorably to the peer median.

      Austin Associates also compared selected operating results of NBT to those of 10 other publicly traded banking organizations headquartered in the mid-Atlantic region (including New York, Washington D.C., Delaware, Maryland, New Jersey and Pennsylvania) having assets between $3 billion and $8 billion. This peer group consisted of the following companies:

      Austin Associates considers this group of financial institutions comparable to NBT as to financial characteristics and stock trading volume. Austin Associates compared selected balance sheet data, asset quality, capitalization, profitability ratios and market statistics. Selected results of this comparison are set forth below:

      This summary indicates that NBT performs above the peer group in financial ratios related to profitability and efficiency, and operates with slightly less capital than the peer median. The following presents a summary of the stock trading levels of NBT compared to this same peer group:

      This comparison indicated that NBT trades at a slight discount to the guideline group’s price to earnings multiple. NBT’s price to tangible book and dividend yield approximate the guideline group.

      Comparable Transaction Analysis. Austin Associates reviewed certain information relating to selected New York bank sale transactions with seller’s assets from $100 million to $1 billion. Austin Associates also reviewed mid-Atlantic bank sale transactions with seller’s assets from $300 million to $1 billion. For the New York and mid-Atlantic transactions, Austin Associates reviewed announced transactions from January 1, 2003 through June 12, 2005. Austin Associates compared the financial performance of the selling institution and prices paid in the selected transactions to CNB’s financial performance and the transaction multiples being paid by NBT for CNB. The following highlights the guideline transaction comparison:

      The multiples being paid by NBT for CNB are above the New York guideline transactions and slightly below the median multiples paid for the mid-Atlantic based banks over the time period considered.

      Contribution Analysis. Austin Associates compared the pro forma ownership interest in NBT that CNB shareholders would receive, in the aggregate, to the contribution by CNB to certain balance sheet and income statement measures of NBT on a pro forma basis. The results of this analysis have been calculated based on an all-stock exchange which simplifies the comparison. The following table compares the range of pro forma ownership of CNB and NBT shareholders in the combined company, with each company’s respective contribution of various selected measures:

      Pro Forma Equivalent Per Share Results. Austin Associates also reviewed the pro forma effect of the proposed transaction to CNB’s last twelve months earnings per share, tangible book value per share and dividends per share. For purposes of this analysis, Austin Associates assumed an all-stock exchange.

      CNB recorded core earnings per share of $1.86 during the last twelve months ending March 31, 2005, and NBT’s core earnings per share measured $1.53 per share. Core earnings per share excludes the after-tax effect from the gain recorded on the sale of securities. Giving effect to the merger, the equivalent CNB earnings would have equaled $2.44 per share, before purchase accounting adjustments, an increase of 30.9 percent from actual results.

      CNB’s tangible book value per share equaled $14.65 as of March 31, 2005 and NBT’s tangible book value measured $8.25 per share. Giving effect to the merger, the equivalent CNB tangible book value would have equaled $13.64, before purchase accounting adjustments, a decrease of 6.9 percent from actual results.

      CNB’s dividends per share over the last twelve months ending March 31, 2005 equaled $0.81 per share. The last twelve months dividend paid by NBT measured $0.76 per share. Based on the current exchange ratio, equivalent dividends per share to CNB shareholders would have measured $1.25 for the twelve month period ending March 31, 2005, representing an increase of 53.9 percent from actual results.

      The opinion expressed by Austin Associates was based on market, economic and other relevant considerations as they existed and could be evaluated as of the date of the opinion. Events occurring after the date of issuance of the opinion, including, but not limited to, changes affecting the securities markets, the results of operations or material changes in the financial condition of either NBT or CNB could materially affect the assumptions used in preparing this opinion.

      CNB has agreed to pay Austin Associates customary fees for its services as financial adviser in connection with the merger. In addition to its fees and regardless of whether the merger is consummated, CNB has agreed to reimburse Austin Associates for its reasonable out-of-pocket expenses, and to indemnify Austin Associates against certain liabilities, including liabilities under securities laws.

Termination and Amendment of the Merger Agreement

      The merger agreement may be terminated prior to the closing, before or after approval by CNB’s stockholders, as follows:

      Under the latter two scenarios described above, if the merger agreement is terminated, CNB shall pay to NBT a fee of $4,500,000. The fee would also be payable to NBT if CNB enters into a merger agreement with a third party within twelve months of the termination of the merger agreement, if the termination was due to a willful breach of a representation, warranty, covenant or agreement by CNB or the failure of the stockholders of CNB to approve the merger agreement after CNB received a third party acquisition proposal.

      Additionally, CNB may terminate the merger agreement if, at any time during the five-day period commencing on the first date on which all bank regulatory approvals (and waivers, if applicable) necessary for consummation of this merger have been received (disregarding any waiting period), such termination to be effective thirty days thereafter if both of the following conditions are satisfied:

      If CNB elects to exercise its termination right as described above, it must give prompt written notice thereof to NBT. During the five-day period commencing with its receipt of such notice, NBT shall have the option to increase the consideration to be received by the holders of CNB common stock by adjusting the exchange ratio to one of the following quotients at its sole discretion: (i) a quotient, the numerator of which is equal to the product of the Initial NBT market value, 1.64, and the index ratio, and the denominator of which is equal to the NBT market value on the determination date; or (ii) a quotient determined by dividing the product of 1.394 and the Initial NBT market value by the NBT market value on the determination date. Because the formula is dependent on the future price of NBT’s common stock and that of the index group, it is not possible presently to determine what the adjusted exchange ratio would be at this time, but, in general, the ratio would be increased and, consequently, more shares of NBT common stock issued, to take into account the extent the average price of NBT’s common stock exceeded the decline in the average price of the common stock of the index group.

      The merger agreement may be amended by the parties at any time before or after approval of the merger agreement by the CNB stockholders. However, after such approval, no amendment may be made without the approval of the CNB stockholders if it reduces the amount or value, or changes the form of, the merger consideration.

      The parties may waive any of their conditions to closing, unless they may not be waived under law.

Material Federal Income Tax Consequences

      The following summary discusses the material federal income tax consequences of the merger to CNB shareholders. The summary is based on the Internal Revenue Code of 1986, as amended, referred to in this section as the Code, the U.S. Treasury regulations promulgated under the Code and related administrative interpretations and judicial decisions, all as in effect as of the effective time of the merger, and all of which are subject to change, possibly with retroactive effect.

      The summary assumes that the holders of shares of CNB’s common stock hold their shares as capital assets. The summary applies only to holders of shares of CNB common stock that are U.S. persons. For purposes hereof, a U.S. person is:

      This summary is not binding on the Internal Revenue Service and there can be no assurance that the Internal Revenue Service will not take a position contrary to one or more of the positions reflected in this summary or that these positions will be upheld by the courts if challenged by the Internal Revenue

Service. No ruling from the Internal Revenue Service has been or will be requested with respect to the merger.

      The summary does not address the tax consequences that may be applicable to particular CNB shareholders in light of their individual circumstances or to CNB shareholders who are subject to special tax rules, including:

      This summary is for general information purposes only. It is not a complete analysis or discussion of all potential effects of the merger. It also does not address any consequences arising under the tax laws of any state, locality, or foreign jurisdiction or under any federal laws other than those pertaining to the federal income tax.

      The merger will be treated for federal income tax purposes as a reorganization within the meaning of Section 368(a) of the Code. The federal tax consequences of the merger to you will depend primarily on whether you exchange your CNB common stock solely for NBT common stock (except for cash received instead of a fractional share of NBT common stock), solely for cash or for a combination of stock and cash.

      Exchange Solely for Cash. In general, if, pursuant to the merger, a holder exchanges all of the shares of CNB common stock actually owned by it solely for cash, that holder will recognize gain or loss equal to the difference between the amount of cash received and its adjusted tax basis in the shares of CNB common stock surrendered. Any such gain or loss generally will be long-term capital gain or loss if the holder’s holding period with respect to the CNB common stock surrendered is more than one year at the effective time of the merger, and otherwise will be short-term capital gain or loss. Individuals generally qualify for favorable tax rates on long-term capital gains. If, however, any such holder constructively owns CNB common stock that is exchanged for NBT common stock in the merger, or otherwise owns NBT common stock actually or constructively after the merger, the consequences to such holder may be similar to the consequences described below under the heading “Exchange for NBT Common Stock and Cash,” except that the amount of consideration, if any, treated as a dividend may not be limited to the amount of such holder’s gain.

      Exchange Solely for NBT Common Stock. If, pursuant to the merger, a holder exchanges all of the shares of CNB common stock actually owned by it solely for shares of NBT common stock, that holder will not recognize any gain or loss except in respect of cash received instead of a fractional share of NBT common stock (as discussed below). The aggregate adjusted tax basis of the shares of NBT common stock received in the merger (including fractional shares deemed received and redeemed as described below) will be equal to the aggregate adjusted tax basis of the shares of CNB common stock surrendered

for the NBT common stock, reduced by the adjusted tax basis allocable to any fractional shares deemed received in the merger as described below. The holding period of the NBT common stock (including fractional shares deemed received and redeemed as described below) will include the period during which the shares of CNB common stock were held.

      Exchange for NBT Common Stock and Cash. If, pursuant to the merger, a holder exchanges all of the shares of CNB common stock actually owned by it for a combination of NBT common stock and cash, the holder will generally recognize gain (but not loss) in an amount equal to the lesser of (1) the amount of gain realized (i.e., the excess of the sum of the amount of cash and the fair market value of the NBT common stock received pursuant to the merger over that holder’s adjusted tax basis in its shares of CNB common stock surrendered) and (2) the amount of cash received pursuant to the merger. For this purpose, gain or loss must be calculated separately for each identifiable block of shares surrendered in the exchange, and a loss realized on one block of shares may not be used to offset a gain realized on another block of shares. Any recognized gain will generally be long-term capital gain if the holder’s holding period with respect to the CNB common stock surrendered is more than one year at the effective time of the merger, and otherwise will be short-term capital gain. Individuals generally qualify for favorable tax rates on long-term capital gains. If, however, the cash received has the effect of the distribution of a dividend, the gain will be treated as a dividend to the extent of the holder’s ratable share of CNB’s accumulated earnings and profits as calculated for United States federal income tax purposes. See “— Possible Treatment of Cash as a Dividend” below.

      The aggregate tax basis of NBT common stock received (including fractional shares deemed received and redeemed as described below) by a holder that exchanges its shares of CNB common stock for a combination of NBT common stock and cash pursuant to the merger will be equal to the aggregate adjusted tax basis of the shares of CNB common stock surrendered, reduced by the amount of cash received by the holder pursuant to the merger (excluding any cash received instead of a fractional share of NBT common stock), and increased by the amount of gain (including any portion of the gain that is treated as a dividend as described below but excluding any gain or loss resulting from the deemed receipt and redemption of fractional shares described below), if any, recognized by the holder on the exchange. The holding period of the NBT common stock (including fractional shares deemed received and redeemed as described below) will include the holding period of the shares of CNB common stock surrendered.

      Possible Treatment of Cash as a Dividend. In general, the determination of whether the gain recognized in the exchange will be treated as capital gain or has the effect of a distribution of a dividend depends upon whether and to what extent the exchange reduces the holder’s deemed percentage stock ownership of NBT. As discussed below, however, dividend treatment will generally not apply to a minority shareholder in a publicly held corporation whose relative stock interest is minimal and who exercises no control with respect to corporate affairs. Gain recognized by such a holder will generally be treated as capital gain.

      For purposes of this determination, the holder is treated as if it first exchanged all of its shares of CNB common stock solely for NBT common stock and then NBT immediately redeemed (the “deemed redemption”) a portion of the NBT common stock in exchange for the cash the holder actually received. The gain recognized in the deemed redemption will be treated as capital gain if the deemed redemption is (1) “substantially disproportionate” with respect to the holder or (2) “not essentially equivalent to a dividend.”

      The deemed redemption will generally be “substantially disproportionate” with respect to a holder if the percentage of the voting power and value of the NBT common stock actually or constructively owned by such holder immediately after the deemed redemption is less than 80% of both the voting power and the value of the NBT common stock actually or constructively owned by such holder immediately before the deemed redemption.

      Whether the deemed redemption is “not essentially equivalent to a dividend” with respect to a holder will depend upon the holder’s particular circumstances. At a minimum, however, in order for the deemed redemption to be “not essentially equivalent to a dividend,” the deemed redemption must result in a

“meaningful reduction” in the holder’s deemed percentage stock ownership of NBT. In general, that determination requires a comparison of (1) the percentage of the voting power and value of the NBT common stock actually or constructively owned by such holder immediately before the deemed redemption and (2) the voting power and the value of the NBT common stock actually or constructively owned by such holder immediately after the deemed redemption. The Internal Revenue Service has ruled that a minority shareholder in a publicly held corporation whose relative stock interest is minimal and who exercises no control with respect to corporate affairs is generally considered to have a “meaningful reduction” even if that shareholder has a relatively minor reduction in its percentage stock ownership under the above analysis.

      If the tests above for capital gain treatment are not met, the recognized gain will be treated as dividend income to the extent of the holder’s ratable share of CNB’s accumulated earnings and profits. Individuals generally qualify for favorable tax rates on dividends.

      In applying the foregoing tests, the constructive ownership rules of section 318 of the Code apply in comparing the holder’s ownership interest in NBT both immediately after the merger (but before the hypothetical redemption) and after the hypothetical redemption. Under these constructive ownership rules, a holder is deemed to own NBT common stock that is actually owned (and in some cases constructively owned) by certain related individuals and entities, and is also deemed to own NBT common stock that may be acquired by such holder or such related individuals or entities by exercising an option, including an employee stock option. Moreover, the tests are applied after taking into account any related transactions undertaken by a shareholder under a single, integrated plan. Thus, dispositions or acquisitions by a holder of NBT common stock before or after the merger that are part of such holder’s plan may be taken into account. As these rules are complex, each holder that may be subject to these rules should consult its tax advisor.

      Cash Received Instead of a Fractional Share. A holder who receives cash instead of a fractional share of NBT common stock will generally be treated as having received such fractional share and then as having received such cash in redemption of the fractional share. Gain or loss generally will be recognized based on the difference between the amount of cash received instead of the fractional share and the portion of the holder’s aggregate adjusted tax basis of the share of CNB common stock surrendered which is allocable to the fractional share. Such gain or loss generally will be long-term capital gain or loss if the holding period for such shares of CNB common stock is more than one year at the effective time of the merger.

      Information Reporting and Backup Withholding. Unless an exemption applies, the exchange agent will be required to withhold, and will withhold, 28% of any cash payments to which a CNB shareholder or other payee is entitled pursuant to the merger, unless the shareholder or other payee provides his or her tax identification number (social security number or employer identification number) and certifies that the number is correct. Each shareholder and, if applicable, each other payee, is required to complete and sign the Form W-9 that will be included as part of the transmittal letter to avoid being subject to backup withholding, unless an applicable exemption exists and is proved in a manner satisfactory to NBT and the exchange agent.

      The federal income tax consequences set forth above are based upon present law and do not purport to be a complete analysis or listing of all potential tax effects that may apply to a holder of CNB’s common stock. The tax effects that are applicable to a particular holder of CNB common stock may be different from the tax effects that are applicable to other holders of CNB common stock, including the application and effect of state, local and other tax laws other than those pertaining to the federal income tax, and thus, holders of CNB common stock are urged to consult their own tax advisors.

      Options. As described above in the section titled “Merger Consideration — CNB Stock Options,” holders of incentive stock options to purchase CNB common stock that are outstanding at the effective time of the merger will have their CNB options converted into options to purchase shares of NBT common stock. The assumption of the options by NBT should not be a taxable event and former holders of CNB options who hold options to purchase NBT common stock after the merger should be subject to

the same federal income tax treatment upon exercise of those options as would have applied if they had exercised their CNB options.

      Holders of CNB options are urged to consult their own tax advisors as to the specific tax consequences to them of the merger, including tax return reporting requirements, available elections, the applicability and effect of federal, state, local and other applicable tax laws, and the effect of any proposed changes in the tax laws.

Accounting Treatment

      The merger, if completed, will be treated as a purchase by NBT of CNB for accounting purposes. Accordingly, under accounting principles generally accepted in the United States, the assets and liabilities of CNB will be recorded on the books of NBT at their respective fair values at the time of the consummation of the merger.

Resales of NBT’s Common Stock Received in the Merger

      NBT is registering the issuance of the shares of its common stock to be exchanged in the merger under the Securities Act. The shares will be freely transferable under the Securities Act, except for shares received by CNB shareholders who are affiliates of CNB or NBT at the time of the special meeting. These affiliates only may resell their shares pursuant to an effective registration statement under the Securities Act covering the shares, in compliance with Securities Act Rule 145 or under another exemption from the Securities Act’s registration requirements. This proxy statement/ prospectus does not cover any resales of NBT’s common stock by NBT or CNB affiliates. Affiliates will generally include individuals or entities who control, are controlled by or are under common control with CNB or NBT, and may include officers or directors, as well as principal shareholders of CNB or NBT.

Employee Benefits

      Employees of CNB who become employees of NBT or a subsidiary of NBT after the merger will (i) be eligible for employee benefits that NBT or a subsidiary of NBT, as the case may be, provides to its employees generally and, except as set forth in the next paragraph, on substantially the same basis as is applicable to similarly situated employees, (ii) be given credit with respect to the satisfaction of the limitations as to pre-existing condition exclusions, evidence of insurability requirements and waiting periods for participation and coverage under NBT’s group health, life insurance and disability plans equal to the credit that any such employee had received as of the effective time towards the satisfaction of any such limitations and waiting periods under the comparable plans of CNB, and (iii) will have waived preexisting condition limitations to the same extent waived under the corresponding CNB plan.

      CNB full-time employees who are not offered full-time employment with NBT or any of its subsidiaries as of the closing date of the merger or who are terminated by NBT or an employing subsidiary of NBT Bank within one year following the closing date of the merger, will be eligible to receive severance benefits equal to one week base pay for each year of employment by CNB at a rate of pay equal to such employee’s base pay as of the termination date (with a minimum payment amount of two weeks’ base pay). Any CNB officer or employee who is terminated by NBT or an employing subsidiary of NBT later than one year following the closing of the merger will be eligible for benefits in accordance with the general severance policy maintained by NBT, provided that such persons will receive credit for prior employment with CNB as if such persons were employed by NBT or a subsidiary of NBT for such period of time.

Dissenters’ Appraisal Rights

      Sections 623 and 910 of the New York Business Corporation Law provide that if the merger is consummated, CNB stockholders who object to the merger and who follow the procedures specified in Section 623 will have the right to receive cash payment of the fair value of their shares. A copy of Section 623 of the NYBCL is attached to this joint proxy statement/ prospectus as Appendix C. The

express procedures of New York Law must be followed precisely; if they are not, stockholders may lose their right to dissent. As described more fully below, such “fair value” would potentially be determined in judicial proceedings, the result of which cannot be predicted. There can be no assurance that stockholders exercising dissenters’ rights of appraisal will receive consideration equal to or greater than the value of the NBT common stock to be owned by them following consummation of the merger.

      The statutory procedures outlined below are complex. Stockholders wishing to exercise their dissenters’ rights should consult their own legal advisors.

      Any CNB stockholder who is entitled to vote on the merger will have the right to receive cash payment of the fair value of his or her shares and the other rights and benefits provided in Section 623 if such stockholder does not vote in favor of the merger and (before the applicable vote of stockholders on the merger) files with CNB written objection to the merger, including in that written objection notice of his or her election to dissent, his or her name and residence address, the number of shares as to which he or she dissents, and a demand for payment of the fair value of such shares if the merger is consummated. A vote against the merger will not satisfy the requirement of filing a written objection. Failure to vote against the merger will not waive a stockholder’s right to payment if the stockholder has filed a written objection and has not voted in favor of the merger. If a stockholder abstains from voting on the merger, this will not waive dissenter’s rights so long as the appropriate written objection to the merger is properly and timely filed. All notices of election to dissent should be addressed to CNB, Attention: Corporate Secretary, at 10-24 North Main Street, P.O. Box 873, Gloversville, NY 12078.

      If an executed proxy is received but no direction is indicated as to how such proxy is to be voted, the shares represented by such proxy will be voted in favor of the merger. Accordingly, the submission of such an unmarked proxy, unless revoked prior to its being voted, will serve to waive dissenter’s rights.

      Within ten days after the date the merger is approved by the stockholders of CNB, CNB will give written notice of such approval by registered mail to each stockholder who filed written objection, except for any stockholder who voted in favor of the merger. A CNB stockholder may not dissent as to fewer than all of his or her shares, held by him or her of record, that he or she owns beneficially. A nominee or fiduciary may not dissent on behalf of any beneficial owner of shares as to fewer than all of said shares of such owner held of record by such nominee or fiduciary.

      Upon consummation of the merger, a dissenting stockholder will cease to have any rights of a stockholder, except the right to be paid the fair value of his or her dissenting shares. A stockholder’s notice of election may be withdrawn at any time prior to his or her acceptance in writing of an offer to purchase his or her dissenting shares by NBT, but in no case may such notice of election be withdrawn later than 60 days after the effective date (unless the company does not make a timely offer) without the consent of NBT. Within one month after the filing of the notice of election to dissent, a dissenting stockholder must submit the certificates representing his or her dissenting shares to CNB, or its transfer agent, which shall note conspicuously on the certificates that such notice of election has been filed, and will then return the certificates to the stockholder. Any stockholder who fails to submit his or her certificates for such notation within 45 days from the date of filing such notice of election to dissent will lose his or her dissenter’s rights unless a court, for good cause shown, otherwise directs.

      Within 15 days after the expiration of the period within which stockholders may file their notices of election to dissent, or within 15 days after the effective date, whichever is later (but in no case later than 90 days after the date of the applicable special meeting), NBT must make a written offer by registered mail to each stockholder who has filed such notice of election to pay for his or her dissenting shares at a specified price which the company considers to be the fair value and, if the merger has been consummated, must accompany such offer by advance payment to each stockholder who has submitted his or her certificates of an amount equal to 80% of the amount of such offer. Such offer must be made at the same price per share to all the dissenting stockholders of CNB. If, within 30 days after the making of such offer, NBT and any dissenting stockholders agree on the price to be paid for dissenting shares, the balance of payment therefor must be made within 60 days after the making of such offer or the effective date, whichever is later, and upon surrender of the certificates representing such shares.

      If NBT fails to make such offer within the 15 day period described above, or if it makes the offer and any dissenting stockholder fails to agree within the period of 30 days thereafter upon the price to be paid for his or her shares, the company is required within 20 days after the expiration of whichever is the applicable of the two periods to institute a special proceeding in the Supreme Court of the State of New York, County of Fulton, to determine the rights of dissenting stockholders and to fix the fair value of their dissenting shares. If NBT fails to institute such proceeding within such 20 day period, any dissenting stockholder may institute a proceeding for the same purpose not later than 30 days after the expiration of such 20 day period. If the dissenting stockholder does not institute such a proceeding within such 30 day period, his or her dissenter’s rights are lost unless the court, for good cause shown, otherwise directs.

      During each proceeding, the court will determine whether each dissenting stockholder is entitled to receive payment for his or her shares and, if so, will fix the value of such shares as of the close of business on the day prior to the applicable special meeting, taking into consideration the nature of the merger transaction giving rise to the stockholder’s right to receive payment for his or her dissenting shares and other relevant factors. The court will also award interest on such amount to be paid from the effective date of the merger to the date of payment unless the court finds that a stockholder’s refusal to accept an offer for payment was arbitrary, vexatious, or otherwise not in good faith. Each party to such proceeding will bear its own costs unless the court finds that such refusal by any stockholder was arbitrary, vexatious, or otherwise not in good faith, in which case NBT’s costs will be assessed against such stockholder. The court, in its discretion, may also apportion or assess any part of the dissenting stockholder’s costs against NBT if it finds that the fair value of the shares determined materially exceeds the amount which the company offered to pay, or that no offer or advance payment was made by the company, or that the company failed to institute such special proceeding, or that the actions of the company in complying with its obligations under Section 623 were arbitrary, vexatious, or otherwise not in good faith. Within 60 days following the final determination of the applicable proceeding, NBT shall pay to each dissenting stockholder the amount found to be due him or her upon the stockholder’s surrender of all certificates representing dissenting shares.

      The enforcement by a stockholder of his or her right to receive payment for shares in accordance with Section 623 excludes the enforcement by such stockholder of any other right to which he or she might otherwise be entitled by virtue of his or her ownership of shares (unless such stockholder withdraws his or her notice of election as provided in Section 623 or the merger is abandoned), except that such stockholder will retain the right to bring or maintain an appropriate action to obtain relief on the grounds that the merger will be or is unlawful or fraudulent as to him or her.

Voting Agreement

      CNB’s officers and directors entered into voting agreements. These voting agreements require the officers and directors to vote all of the shares of CNB common stock beneficially owned by them in favor of the merger.

      As of the record date, the CNB shareholders who entered into voting agreements collectively held shares of CNB common stock which represented approximately 6% of the outstanding CNB common stock. None of the CNB officers and directors who are parties to the voting agreements were paid additional consideration in connection with the execution of such agreements.

Interests of CNB Directors and Executive Officers in the Merger That are Different Than Yours

      Some of the members of CNB’s management and board of directors have financial interests in the merger that are in addition to their interests as stockholders of CNB. The CNB board was aware of these interests and considered them, among other matters, in approving the merger agreement.

      CNB currently has change of control agreements with each of William Smith and George Morgan and an agreement for supplemental retirement benefits with William Smith, each of which will be

terminated upon the closing of the merger and superseded by new agreements and general releases as described below.

      Change of Control Agreements. Under Messrs. Smith and Morgan’s existing change of control agreements, if a change of control occurs while the executive is employed by CNB, CNB will continue to employ the executive in the same capacity or position (unless otherwise agreed in writing) until the fifth anniversary of the change of control. During this employment period, the executive would receive an annual salary not less than the executive’s annual salary as in effect as of the date of the change of control, subject to certain adjustments. If the executive’s employment was terminated by CNB other than by reason of death or disability or cause or the executive resigned for good reason during the term of the agreement following a change of control, the executive would be entitled to receive a lump sum cash payment equal to the product of (i) the employee’s annual salary as in effect on the date of the change of control (adjusted to reflect annual compensation adjustments) plus (ii) the highest incentive compensation earned by the executive during the twenty-four months ended on the date of termination, times (iii) the lesser of three or the number of years remaining in the employment period. In addition, in the event that any payments and distributions to Messrs. Smith and Morgan are subject to the excise tax imposed by Section 4999 of the Internal Revenue Code, CNB would be required to make a gross-up payment to the executive so that the executive would have been placed in the same after-tax position as if no excise tax had been imposed.

      Agreement for Supplemental Retirement Benefits. Under Mr. Smith’s existing agreement for supplemental retirement benefits, Mr. Smith is entitled to receive additional retirement benefits that cannot be provided under the qualified retirement plans due to tax law limitations. Under the agreement, Mr. Smith is entitled, upon reaching his normal retirement date, to receive a supplemental pension benefit and a supplemental profit sharing benefit corresponding to that portion of his pension benefits and profit sharing benefits that exceed the compensation limitation under Section 401(a)(17) of the Internal Revenue Code.

      Concurrently with entering into the merger agreement, City National Bank and Trust Company, NBT, and each of Messrs. Smith and Morgan entered into new agreements and general releases, which generally become effective only upon completion of the merger. In the event the merger agreement is terminated, these agreements and general releases will automatically be terminated and be null and void.

      Under the terms of these agreements, upon the closing under the merger agreement, the change of control agreements with Messrs. Smith and Morgan and the agreement for supplemental retirement benefits with Mr. Smith will be automatically terminated. Instead, on the closing date, Messrs. Smith and Morgan will be provided with lump sum cash payments of $956,568.18 and $644,453.34, respectively, less tax withholding and other deductions required by law. Mr. Smith will also receive a single lump sum cash payment (less tax withholding and other deductions required by law) of an amount equal to the sum of the supplemental profit sharing plan benefit and supplemental pension benefit payable or earned by Mr. Smith through the date of the closing. Messrs. Smith and Morgan are entitled to receive an additional payment to make them whole for any excise tax owed under Section 280G of the Code as a result of the lump sum payments.

      In addition, under the terms of these agreements, Messrs. Smith and Morgan will receive (i) all retirement benefits accrued by him under the terms of CNB’s tax-qualified pension and profit sharing plans, (ii) the continued right to exercise any incentive stock options assumed by NBT pursuant to the merger agreement, (iii) the continued right to exercise through the date of closing any vested non-qualified stock options for shares of CNB common stock held, and the right to receive the option payments described in the merger agreement in exchange for any vested non-qualified stock options for shares of CNB common stock not exercised prior to closing, (iv) continued coverage under CNB’s group health plan and other employee welfare benefit plans through the date his eligibility for such plans as an employee of CNB ends, (v) continued coverage under life insurance policies provided by CNB or its

successor, (vi) continued use of a CNB automobile until closing, at which point the automobile will be transferred to the executive, and (vii) in the case of Mr. Morgan only, post-retirement group life and health coverage on the same terms available to other similarly situated retired employees of CNB or NBT until the earlier of age 65 or the time he becomes eligible for coverage under another employer’s group health plan.

      Each of Messrs. Smith and Morgan have agreed not to compete with NBT or NBT Bank for a period of five years following completion of the merger. As partial consideration for the lump sum cash payments under the agreements, Messrs. Smith and Morgan have agreed to provide transition services to NBT Bank for the two month period following the closing of the merger as the president or board of directors of NBT Bank may reasonably direct. Messrs. Smith and Morgan have agreed further not to disclose any confidential information regarding CNB or NBT following the merger.

      In connection with entering into the merger agreement, City National Bank and Trust Company and each of Messrs. Frank, Bradt and Doherty entered into new retention agreements in order to ensure the seamless transition of the transactions contemplated pursuant to the merger agreement by retaining the services of these individuals through the closing date and for the one-year period thereafter. If the employee is terminated during such one-year period, the employee will receive a one-time lump sum cash payment equal to the employee’s annual base salary as of his termination date if the employee is terminated by NBT without cause at any time during the one-year period following the closing of the merger. In the event the merger agreement is terminated, these retention agreements will automatically be terminated and be null and void.

      Upon consummation of the merger, Messrs. Delaney and Hanaburgh will be appointed to the Board of Directors of NBT Bank with a term of office expiring at the first annual meeting of stockholders of NBT Bank to be held following the consummation of the merger.

      Effective on the consummation of the merger, NBT will establish the Fulton County Advisory Board. Each person who served on the Board of Directors of CNB, other than Messrs. Delaney and Hanaburgh, shall be appointed to the Advisory Board. It is anticipated that the Advisory Board will meet between six and ten times per year, and that each Advisory Board member will receive a fee of $1,000 for each meeting attended.

      NBT has agreed to indemnify and hold harmless each of CNB’s present and former directors, officers and employees for a period of six years from the effective time of the merger from costs and expenses arising out of matters existing or occurring at or before the consummation of the merger to the fullest extent allowed under applicable law and the certificate of incorporation and bylaws of NBT. NBT has also agreed that it will maintain CNB’s existing directors’ and officers’ liability insurance policy, or provide a policy providing similar coverage, for the benefit of CNB’s directors and officers who are currently covered by such insurance, for at least three years from the effective time of the merger, with respect to acts or omissions occurring prior to the effective time of the merger, subject to a limit on the cost to maintain such coverage.

SECURITY OWNERSHIP OF MANAGEMENT AND

CERTAIN BENEFICIAL OWNERS OF CNB

      The following table provides information as of July 13, 2005 about the shares of CNB common stock that may be considered beneficially owned by each named executive officer and director, and all directors and executive officers of CNB as a group. As of June 30, 2005, no person beneficially owns more than 5% of CNB’s outstanding common stock.

COMPARISON OF STOCKHOLDER RIGHTS

AND DESCRIPTION OF CAPITAL STOCK

Comparison of Stockholders’ Rights

      Upon completion of the merger, the stockholders of CNB will become stockholders of NBT. The rights of CNB stockholders are presently governed by New York law and the CNB restated certificate of incorporation and bylaws. After the merger the rights of former CNB stockholders will be governed by Delaware law and the NBT certificate of incorporation and bylaws. The following chart summarizes the material differences between the rights of holders of CNB common stock prior to the merger and after completion of the merger when the former CNB stockholders will be NBT stockholders. This summary does not purport to be complete and we qualify the summary in its entirety by reference to the CNB articles of incorporation and bylaws, the NBT certificate of incorporation and bylaws, and the relevant provisions of New York and Delaware law. You can obtain copies of the governing corporate instruments of NBT and CNB, without charge, by following the instructions listed under “Where You Can Find More Information.”

Description of NBT Capital Stock