1


                                                                       Exhibit 5


          (517) 371-8100

                                   May 6, 1998



Commercial National Financial Corporation
101 N. Pine River Street
Ithaca, MI  48847

Gentlemen:

                  RE:      Registration Statement on Form S-8

                  In connection with the proposed registration of 50,000 shares
of common stock of Commercial National Financial Corporation (the "Corporation")
covered by the above-captioned Registration Statement, we have examined the
Corporation's Articles of Incorporation, Bylaws, Corporate Minute Book and the
Registration Statement to be filed with the Securities and Exchange Commission
pursuant to the Securities Act of 1933 on or about May 11, 1998.

                  Based upon such examination and upon examination of such other
instruments and records as we deem necessary, we are of the opinion that:

                  1. The Corporation has been duly incorporated under the laws
of the State of Michigan, and is validly existing and in good standing under the
laws of that state.

                  2. The 50,000 shares of common stock covered by this
Registration Statement have been legally authorized and when such shares have
been duly delivered against payment therefore as contemplated by the Commercial
National Financial Corporation 1991 Stock Option Plan, such shares will be
legally issued, fully paid and nonassessable.


   2


Commercial National Financial Corporation
May 6, 1998
Page 2


                  This opinion is furnished for use as an exhibit to the
Registration Statement. We hereby consent to the filing of this opinion as an
exhibit.

                                       Very truly yours,

                                       FOSTER, SWIFT, COLLINS & SMITH, P.C.



                                       /s/ Foster, Swift, Collins & Smith, P.C.