1 Exhibit 5.1 Patterson, Belknap, Webb & Tyler LLP 1133 Avenue of the Americas New York, NY 10036-6710 212-336-2000 Fax 212-336-2222 Christopher C. Angell Robert W. Lehrburger Of Counsel Douglas E. Barzelay Jeffrey I.D. Lewis Susan F. Bloom Robert P. LoBue Harold R. Tyler, Jr. Henry P. Bubel Ellen M. Martin William F. Cavanaugh, Jr. Maureen W. McCarthy Lisa E. Clearly Thomas C. Morrison Robert J. Egan Edward F. Cox Bernard F. O'Hare Robert H. M. Ferguson John Delli Venneri Gloria C. Phares George S. Frazza John M. DiMatteo Thomas W. Pippert Robert M. Pennoyer Gregory L. Diskant Dennis W. Russo Robert B. Shea David F. Dobbins Peter J. Schaeffer Evelyn M. Sommer David W. Dykhouse Andrew D. Schau Ira T. Wender, P.C. Philip R. Forlenza John E. Schmeltzer, III Eugene M. Gelernter John P. Schmitt Alan Gettner Stephen W. Schwarz David M. Glaser Arthur D. Sederbaum Writer's direct line Antonia M. Grumbach Karl E. Seib, Jr. Dana W. Hiscock Saul B. Shapiro Scott Horton Richard R. Upton Karen C. Hunter Frederick B. Warder III Rochelle Korman William W. Weisner Robin Krause John D. Winter Jeffrey E. LaGueux Stephen P. Younger Kim J. Landsman Steven A. Zalesin - January 25, 2001 Dime Bancorp, Inc. 589 Fifth Avenue New York, New York 10017 Dear Sirs: We have acted as counsel to Dime Bancorp, Inc., a Delaware corporation (the "Company"), in connection with the proposed registration by the Company under the Securities Act of 1933, as amended (the "Act"), of 1,314,000 shares (the "Shares") of the Company's Common Stock, par value $.01 per share (the "Common Stock"), pursuant to the Company's Registration Statement on Form S-8 (the "Registration Statement") filed with the Securities and Exchange Commission (the "Commission") on the date hereof. 2 Page 2 In rendering this opinion we have examined the Company's Certificate of Incorporation and Bylaws, each as amended to date, and the minutes of the corporate proceedings taken by the Company in connection with the authorization of the Shares. We have also examined the originals, or copies certified or otherwise identified to us, of the corporate records of the Company, certificates of public officials and representatives of the Company, and such other documents and records, and have made such investigations of law, as we have deemed necessary for purposes of this opinion. We have assumed the genuineness of all signatures, the conformity to the original of all copies and the factual accuracy of all certificates submitted to us. On the basis of the foregoing, we are of the opinion that the Shares have been duly authorized by all necessary corporate action on the part of the Company and when sold and delivered as contemplated by the Registration Statement will constitute duly authorized, validly issued, fully paid and nonassessable shares of Common Stock. We express no opinion as to laws other than the corporate laws of the State of Delaware and the laws of the United States of America. We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement. In furnishing this opinion and giving this consent, we do not admit that we are in the category of persons whose consent is required under Section 7 of the Act, or the rules and regulations of the Commission thereunder. PATTERSON, BELKNAP, WEBB & TYLER LLP By: /s/ Jeffrey E. LaGueux ---------------------------- A Member of the Firm