<PAGE>   1
    As filed with the Securities and Exchange Commission on December 23, 1999

                                                Registration No. 33-____________
================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8

                             REGISTRATION STATEMENT

                        Under the Securities Act of 1933

                             COMSHARE, INCORPORATED
             (Exact name of registrant as specified in its charter)

          Michigan                                    38-1804887
  (State or other jurisdiction of           (I.R.S. Employer Identification No.)
incorporation or organization)

                 555 Briarwood Circle, Ann Arbor, Michigan 48108
                                 (734) 994-4800
               (Address, including zip code, and telephone number,
                 including area code, of registrant's Principal
                                Executive Office)

                             Comshare, Incorporated
                          Employee Stock Purchase Plan
                            (Full Title of the Plan)

   MICHAEL S. KHOURY, Vice President, General Counsel and Corporate Secretary
                             Comshare, Incorporated
                 555 Briarwood Circle, Ann Arbor, Michigan 48108
                                 (734) 994-4800
 (Name, address, including zip code, and telephone number, including area code,
 of agent for service)

                        Copies of all communications to:

                                THOMAS S. VAUGHN
                               Dykema Gossett PLLC
                             400 Renaissance Center
                          Detroit, Michigan 48243-1668
                                 (313) 568-6524

                         CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------------
       Title of                                         Proposed                Proposed                 Amount of
     Securities to            Amount to be               Maximum                 Maximum               Registration
     be Registered             Registered               Offering                Aggregate                   Fee
                                                    Price Per Share*        Offering Price**
--------------------------------------------------------------------------------------------------------------------
<S>                         <C>                    <C>                     <C>                       <C>
     Common Stock           500,000 shares**           $3.9219                $1,960,950                $517.69
    $1.00 par value
--------------------------------------------------------------------------------------------------------------------
</TABLE>

*        Estimated solely for the purpose of calculating the registration fee,
         based on the average of the high and low sale prices of the Common
         Stock on the NASDAQ National Market on December 22, 1999, in
         accordance with Rule 457(h).
**       The number of shares may be adjusted to prevent dilution from stock
         splits, stock dividends and similar transactions. This Registration
         Statement shall cover any such additional shares in accordance with
         Rule 416(a).
================================================================================
<PAGE>   2
                                    PART II


Item 3.  INCORPORATION OF DOCUMENTS BY REFERENCE


         The following documents filed by Comshare, Incorporated (the "Company")
with the Securities and Exchange Commission ("SEC") are incorporated herein by
reference:

                  (a)      The Company's Annual Report on Form 10-K for the year
                           ended June 30, 1999;

                  (b)      The Company's Quarterly Reports on Form 10-Q for the
                           quarter ended September 30, 1999; and

                  (c)      Description of the Company's Common Stock contained
                           in the Prospectus forming a part of the Company's
                           Registration Statement on Form S-1 (No. 2-29663)
                           (incorporated by reference into the Company's
                           Registration Statement on Form 10 filed under the
                           Securities Exchange Act of 1934 in October 1969, as
                           amended by Item 4 of the Company's Form 8-K Report
                           for January 1973 (SEC File Reference Number 04096),
                           Item 5 of the Company's Form 8-K Report, filed in
                           September 1988 (SEC File Reference Number 04096) and
                           Item 5 of the Company's Form 8-K Report, filed in
                           September 1996).

         All documents filed by the Company with the SEC pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934 subsequent to
the date hereof and prior to the filing of a post-effective amendment which
indicates that all securities being offered have been sold or which deregisters
all securities then remaining unsold shall be deemed to be incorporated by
reference and to be a part hereof from the date of filing of each such document.


Item 4.  DESCRIPTION OF SECURITIES

         The Common Stock to be offered is registered under Section 12 of the
Securities Exchange Act of 1934.


Item 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL

         Not applicable.

Item 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         Sections 561 through 571 of the Michigan Business Corporation Act (the
"MBCA") govern the indemnification of officers, directors and other persons. In
this regard, the MBCA provides for indemnification of directors and officers
acting in good faith and in a manner they reasonably believe to be in, or not
opposed to, the best interest of the Company or its shareholders (and, with
respect to a criminal proceeding, if they have no reasonable cause to believe
their conduct to be unlawful). Such indemnification may be made against (a)
expenses (including attorney's fees), judgments, penalties, fines and amounts
paid in settlement actually and reasonably incurred in connection with any
threatened, pending or completed action, suit or proceeding (other than an
action by, or in the right of the Company) arising by reason of the fact that
they were serving as a director, officer, employee or agent of the Company (or
some other entity at the Company's request), and (b) expenses (including
attorney's fees) and amounts paid in settlement actually and reasonably incurred
in connection with a threatened, pending or completed action or suit by, or in
the right of, the Company (a "Derivative Action"), unless the director or
officer is found liable to the Company and an appropriate court does not
determine that he or she is nevertheless fairly and reasonably entitled to




                                      II-1
<PAGE>   3


indemnification. The MBCA permits the Company to indemnify its officers as set
forth above only on a determination that indemnification is proper because the
applicable standard of conduct has been met. Because the Company's articles of
incorporation eliminate a director's liability for money damages as set forth in
the next paragraph, the MBCA generally permits the Company to indemnify its
directors without any determination that the applicable standard of conduct
as set forth above has been met, except that indemnification for Excluded Acts
(as defined below) only can be authorized by a court of competent jurisdiction
and indemnification of amounts paid in settlement of a Derivative Action only
can be authorized upon a determination that indemnification is proper. A
required determination can be made by action of the board of directors of the
Company, certain members or committees of the board of directors of the Company,
the shareholders of the Company, independent legal counsel or a court of
competent jurisdiction. The MBCA requires indemnification for expenses to the
extent that a director or officer is successful in defending against any action,
suit or proceeding described above. In certain circumstances the MBCA further
requires advances to cover such expenses before a final determination that
indemnification is permissible, upon receipt of (i) a written affirmation by the
director or officer of his or her good faith belief that he or she has met the
applicable standard of conduct set forth in the MBCA, and (ii) a written
undertaking by or on behalf of the director or officer to repay such amounts
unless it shall ultimately be determined that he or she is entitled to
indemnification. The Company's articles of incorporation require the Company to
indemnify officers and directors to the fullest extent authorized by the MBCA as
set forth above.

         Subject to the exceptions recited in the following sentence, pursuant
to Section 209(c) of the MBCA, the Company's articles of incorporation eliminate
a director's liability to the Company or its shareholders for money damages for
any action taken or failure to take any action as a director. Such exculpatory
language does not, however, eliminate or limit the liability of a director for
(a) the amount of a financial benefit received by a director to which he or she
is not entitled, (b) intentional infliction of harm on the Company or its
shareholders, (c) certain other violations of the MBCA, or (d) an intentional
criminal act (the "Excluded Acts").

         The MBCA permits the Company to purchase insurance on behalf of its
directors and officers against liabilities arising out of their positions with
the Company, whether or not such liabilities would be within the indemnification
provisions of the MBCA. Under an insurance policy maintained by the Company, the
directors and officers of the Company are insured, within the limits and subject
to the limitations of the policy, against certain expenses in connection with
the defense of certain claims, actions, suits or proceedings, and certain
liabilities which might be imposed as a result of such claims, actions, suits or
proceedings, which may be brought against them by reason of being or having
served as directors and officers of the Company or certain other entities.

Item 7.  EXEMPTION FROM REGISTRATION CLAIMED

         Not applicable.


Item 8.  EXHIBITS

         The following exhibits are filed with this registration statement:

         4.1  Articles III, V and VI of the Restated Articles of Incorporation
              of the Registrant, as amended - incorporated by reference to
              Exhibit 3.01 to the Registrant's Form 10-K Report for the fiscal
              year ended June 30, 1998.

         4.2  Articles III, IV, V, VI and XI of the Restated Bylaws of the
              Registrant, as amended - incorporated by reference to Exhibit
              3.02 to the Registrant's Form 10-K Report for the fiscal year
              ended June 30, 1998.




                                     II-2


<PAGE>   4



          4.3  Specimen form of Common Stock Certificate - incorporated by
               reference to Exhibit 4(c) to the Registrant's Form S-1
               Registration Statement No. 2-29663.

          4.4  Rights Agreement, dated as of September 16, 1996, between
               Comshare, Incorporated and KeyBank National Association, as
               Rights Agent - incorporated by reference to Exhibit 2 to the
               Registrant's Registration Statement on Form 8-A, filed on
               September 17, 1996.

          4.5  Form of certificate representing Rights (included as Exhibit B to
               the form of Rights Agreement filed as Exhibit 4.4). Pursuant to
               the Rights Agreement, Rights Certificates will not be mailed
               until after the earlier of (i) the tenth business day (or such
               later date as may be determined by the Board of Directors, with
               the concurrence of a majority of the Continuing Directors, prior
               to such time as any person becomes an Acquiring Person) after the
               date of the commencement of, or first public announcement of the
               intent to commence, a tender or exchange offer by any person or
               group of affiliated or associated persons (other than the Company
               or certain entities affiliated with or associated with the
               Company), if, upon consummation thereof, such person or group of
               affiliated or associated persons would be the beneficial owner of
               15% or more of such outstanding shares of Common Stock -
               incorporated by reference to Exhibit 1 to the Registrant's
               Registration Statement on Form 8-A, filed on September 17, 1996.

          5    Opinion of Dykema Gossett PLLC with respect to the legality of
               the Common Stock to be registered hereunder.

          23.1 Consent of Arthur Andersen L.L.P.

          23.2 Consent of Dykema Gossett PLLC (contained in Exhibit 5).

          24.1 Power of Attorney of Kathryn A. Jehle.

          24.2 Power of Attorney of Dennis G. Ganster.

          24.3 Power of Attorney of Daniel T. Carroll.

          24.4 Power of Attorney of Geoffrey B. Bloom.

          24.5 Power of Attorney of Richard L. Crandall.

          24.6 Power of Attorney of Alan G. Merten.

          24.7 Power of Attorney of John F. Rockart.

          99.1 Comshare, Incorporated Employee Stock Purchase Plan -
               incorporated by reference to Exhibit 10.20 to the Registrant's
               From 10-Q Report for the quarter ended September 30, 1994.

          99.2 First Amendment to the Comshare, Incorporated Employee Stock
               Purchase Plan - incorporated by reference to Exhibit 10.01 to the
               Registrant's From 10-Q Report for the quarter ended September 30,
               1999.



                                      II-3


<PAGE>   5




          99.3 Second Amendment to the Comshare, Incorporated Employee Stock
               Purchase Plan - incorporated by reference to Exhibit 10.02 to the
               Registrant's From 10-Q Report for the quarter ended September 30,
               1999.

          99.4 Third Amendment to the Comshare, Incorporated Employee Stock
               Purchase Plan - incorporated by reference to Exhibit 10.03 to the
               Registrant's From 10-Q Report for the quarter ended September 30,
               1999.









                                      II-4



<PAGE>   6




Item 9.   UNDERTAKINGS

          (1)  The undersigned registrant hereby undertakes (a) to file, during
any period in which offers or sales are being made, a post-effective amendment
to this registration statement to include any material information with respect
to the plan of distribution not previously disclosed in the registration
statement or any material change to such information in the registration
statement, (b) that, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof, and (c) to remove from registration by means of a
post-effective amendment any of the securities which remain unsold at the
termination of the offering.

          (2)  The undersigned registrant hereby undertakes that, for purposes
of determining any liability under the Securities Act of 1933, each filing of
the registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 that is incorporated by reference in the
registration statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

          (3)  Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
persons of the registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.






                                      II-5



<PAGE>   7



                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Ann Arbor, State of Michigan on December 22, 1999.

                              COMSHARE, INCORPORATED


                              By: /s/ Kathryn A. Jehle
                                  ----------------------------------------------
                                      Kathryn A. Jehle
                              Its:    Senior Vice President, Chief Financial
                                      Officer, Treasurer and Assistant Secretary


     Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
indicated capacities as of December 22, 1999.

  Signature                                      Title
  ---------                                      -----

         *                     Director, President and Chief Executive Officer
-----------------------------
Dennis G. Ganster


/s/ Kathryn A. Jehle           Director, Senior Vice President, Chief Financial
-----------------------------  Officer, Treasurer and Assistant Secretary
Kathryn A. Jehle

         *                     Director and Chairman of the Board
-----------------------------
Daniel T. Carroll

         *                     Director
-----------------------------
Geoffrey B. Bloom

         *                     Director
-----------------------------
Richard L. Crandall

         *                     Director
-----------------------------
Alan G. Merten

         *                     Director
-----------------------------
John F. Rockart


* By:  /s/ Kathryn A. Jehle
       ----------------------
         Kathryn A. Jehle
         Power-of-Attorney

                                      II-6



<PAGE>   8



                                INDEX TO EXHIBITS
<TABLE>
<CAPTION>


                                                                                                   Sequentially
Number            Description                                                                      Numbered Page
------            -----------                                                                      -------------
<S>               <C>                                                                             <C>

4.1               Articles III, V and VI of the Restated Articles of Incorporation of the
                  Registrant, as amended - incorporated by reference to Exhibit 3.01 to the
                  Registrant's Form 10-K Report for the fiscal year ended June 30, 1998.

4.2               Articles III, IV, V, VI and XI of the Restated Bylaws of the Registrant, as
                  amended - incorporated by reference to Exhibit 3.02 to the Registrant's
                  Form 10-K Report for the fiscal year ended June 30, 1998.

4.3               Specimen form of Common Stock Certificate - incorporated by reference
                  to Exhibit 4(c) to the Registrant's Form S-1 Registration Statement No. 2-
                  29663.

4.4               Rights Agreement, dated as of September 16, 1996, between
                  Comshare, Incorporated and KeyBank National Association, as
                  Rights Agent incorporated by reference to Exhibit 2 to the
                  Registrant's Registration Statement on Form 8-A, filed on
                  September 17, 1996.

4.5               Form of certificate representing Rights (included as Exhibit B to the form
                  of Rights Agreement filed as Exhibit 4.4).  Pursuant to the Rights
                  Agreement, Rights Certificates will not be mailed until after the earlier of (i)
                  the tenth business day (or such later date as may be determined by the
                  Board of Directors, with the concurrence of a majority of the Continuing
                  Directors, prior to such time as any person becomes an Acquiring Person)
                  after the date of the commencement of, or first public announcement of the
                  intent to commence, a tender or exchange offer by any person or group of
                  affiliated or associated persons (other than the Company or certain entities
                  affiliated with or associated with the Company), if, upon consummation
                  thereof, such person or group of affiliated or associated persons would be
                  the beneficial owner of 15% or more of such outstanding shares of
                  Common Stock - incorporated by reference to Exhibit 1 to the Registrant's
                  Registration Statement on Form 8-A, filed on September 17, 1996.

5                 Opinion of Dykema Gossett PLLC with respect to the
                  legality of the Common Stock to be registered
                  hereunder (including consent).

23.1              Consent of Arthur Andersen L.L.P.

24.1              Power of Attorney of Kathryn A. Jehle.

24.2              Power of Attorney of Dennis G. Ganster.

24.3              Power of Attorney of Daniel T. Carroll.

24.4              Power of Attorney of Geoffrey B. Bloom.

24.5              Power of Attorney of Richard L. Crandall.

24.6              Power of Attorney of Alan G. Merten.

24.7              Power of Attorney of John F. Rockart.

99.1              Comshare, Incorporated Employee Stock Purchase Plan - incorporated by reference
                  to Exhibit 10.20 to the Registrant's From 10-Q Report for the quarter ended September 30,
                  1994.

99.2              First Amendment to the Comshare, Incorporated Employee Stock Purchase Plan -
                  incorporated by reference to Exhibit 10.01 to the Registrant's From 10-Q Report for
                  the quarter ended September 30, 1999.

99.3              Second Amendment to the Comshare, Incorporated Employee Stock Purchase Plan -
                  incorporated by reference to Exhibit 10.02 to the Registrant's From 10-Q Report for the
                  quarter ended September 30, 1999.

99.4              Third Amendment to the Comshare, Incorporated Employee Stock Purchase Plan -
                  incorporated by reference to Exhibit 10.03 to the Registrant's From 10-Q Report for the
                  quarter ended September 30, 1999.
</TABLE>