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                                                                     EXHIBIT 5.1

                                November 7, 2000

ScanSoft, Inc.
9 Centennial Drive
Peabody, Massachusetts 01960

        Re:     Registration Statement on Form S-8; ScanSoft, Inc. 2000 Stock
                Plan, ScanSoft, Inc. 2000 Nonstatutory Stock Plan, and ScanSoft,
                Inc. Stand-Alone Stock Option Agreement No. 1.

Ladies and Gentlemen:

        At your request, we are rendering this opinion in connection with the
proposed issuance of an aggregate of 5,500,000 shares of common stock, $0.001
par value (the "Common Stock") of ScanSoft, Inc., a Delaware corporation (the
"Company"), issuable upon the exercise of options granted under the ScanSoft,
Inc. 2000 Stock Plan, the ScanSoft, Inc. 2000 Nonstatutory Stock Plan, and the
ScanSoft, Inc. Stand-Alone Stock Option Agreement No. 1 (together the "Plans").

        We have examined instruments, documents, and records which we deemed
relevant and necessary for the basis of our opinion hereinafter expressed. In
such examination, we have assumed the following: (a) the authenticity of
original documents and the genuineness of all signatures; (b) the conformity to
the originals of all documents submitted to us as copies; and (c) the truth,
accuracy and completeness of the information, representations and warranties
contained in the records, documents, instruments and certificates we have
reviewed.

        Based on such examination, we are of the opinion that the 5,500,000
shares of Common Stock to be issued by the Company pursuant to the Plans are
validly authorized shares of Common Stock and, when issued in accordance with
the provisions of the Plans, will be legally issued, fully paid and
nonassessable.

        We hereby consent to the filing of this opinion as an exhibit to this
Registration Statement on Form S-8 and to the use of our name wherever it
appears in said Registration Statement. In giving such consent, we do not
consider that we are "experts" within the meaning of such term as used in the
Securities Act of 1933, as amended, or the rules and regulations of the
Securities and Exchange Commission issued thereunder, with respect to any part
of the Registration Statement, including this opinion as an exhibit or
otherwise.

                                          Very truly yours,


                                          /s/ Wilson Sonsini Goodrich & Rosati
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                                          Wilson Sonsini Goodrich & Rosati
                                          Professional Corporation