UNITED STATES
                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549

                                   FORM 10-K

(Mark One)

[X]      ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
SECURITIES EXCHANGE ACT OF 1934

      For the fiscal year ended:   December 31, 2004
                                   -----------------

                                      or

[  ]     TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
SECURITIES EXCHANGE ACT OF 1934

      For the transition period from               to
                                     -------------    -------------


                     Commission file number: 333-109248-25
                                             -------------


              CWMBS, Inc., Mortgage Pass-Through Trust 2004-HYB4,
             Mortgage Pass-Through Certificates, Series 2004-HYB4
             ----------------------------------------------------
            (Exact name of Registrant as specified in its charter)


        Delaware                                       95-4449516
---------------------                         ---------------------------
(State or other jurisdiction of           (I.R.S. Employer Identification No.)
incorporation or organization)

c/o   Countrywide Home Loans Servicing LP
      4500 Park Granada

      Calabasas, California                               91302
---------------------------                   ---------------------------
(Address of principal executive offices)               (Zip Code)

Registrant's telephone number, including area code:   (818)225-3000
                                                      -------------

Securities registered pursuant to Section 12(b) of the Act:  None
                                                             ----

Securities registered pursuant to Section 12(g) of the Act:  None
                                                             ----


<PAGE>


     Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to
such filing requirements for the past 90 days. [X] Yes [ ] No

     Indicate by check mark if disclosure of delinquent filers pursuant to
Item 405 of Regulation S-K (ss.229.405 of this chapter) is not contained
herein, and will not be contained, to the best of registrant's knowledge, in
definitive proxy or information statements incorporated by reference in Part
III of this Form 10-K or any amendment to this Form 10-K. [X]

     Indicate by check mark whether the registrant is an accelerated filer (as
defined in Rule 12b-2 of the Act). [ ] Yes [X] No

     State the aggregate market value of the voting and non-voting common
equity held by non-affiliates computed by reference to the price at which the
common equity was last sold, or the average bid and asked price of such common
equity, as of the last business day of the registrant's most recently
completed second fiscal quarter. Not applicable
                                 --------------


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<PAGE>


                      DOCUMENTS INCORPORATED BY REFERENCE

                                     None.

                                     * * *


     This Annual Report on Form 10-K (the "Report") is filed with respect to
the trust fund entitled Mortgage Pass-Through Trust 2004-HYB4 (the "Trust
Fund") formed pursuant to the pooling and servicing agreement dated as of July
1, 2004 (the "Pooling and Servicing Agreement") among CWMBS, Inc., as
depositor (the "Company"), Countrywide Home Loans, Inc., as a seller (a
"Seller"), Belvedere Trust Finance Corporation, as a seller (a "Seller"),
Countrywide Home Loans Servicing LP, as master servicer (the "Master
Servicer"), and The Bank of New York, as trustee (the "Trustee"), for the
issuance of CWMBS, Inc., Mortgage Pass-Through Certificates, Series 2004-HYB4
(the "Certificates"). Certain information otherwise required to be included in
this Report by the Instructions to Form 10-K has been omitted in reliance on
the relief granted to the Company in CWMBS, Inc. (February 3, 1994) (the
"Relief Letter").


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<PAGE>


                                    PART I

Item 1.        Business.

               Not applicable. See the Relief Letter.

Item 2.        Properties.

               Not applicable. See the Relief Letter.

Item 3.        Legal Proceedings.

               There were no material pending legal proceedings relating to
               the Trust Fund to which any of the Trust Fund, the Trustee, the
               Master Servicer or the Company was a party or of which any of
               their respective properties was the subject during the fiscal
               year covered by this Report other than ordinary routine
               litigation incidental to the duties of the Trust Fund, the
               Trustee, the Master Servicer or the Company, nor is the Company
               aware of any such proceedings contemplated by governmental
               authorities.

Item 4.        Submission of Matters to a Vote of Security Holders.

               No matter was submitted to a vote of Certificateholders, and no
               Certificateholder consent was solicited during the fiscal year
               covered by this Report.


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<PAGE>


                                    PART II

Item 5.        Market for Registrant's Common Equity, Related
               Stockholder Matters and Issuer Purchases of Equity
               Securities.

               (a)  Item 201 of Regulation S-K:

                    i.   Market Information. There is no established public
                         trading market for the Certificates.

                    ii.  Holders. As of December 31, 2004 there were less than
                         300 holders of record of the Certificates.

                    iii. Dividends. Not applicable. See the Relief Letter.
                         (Information as to distributions to
                         Certificateholders is provided in the Registrant's
                         monthly filings on Form 8-K.)

                    iv.  Securities Authorized for Issuance Under Equity
                         Compensation Plans. Not applicable.

                    Item 701 of Regulation S-K. Not applicable.

               (b)  Rule 463 of the Securities Act of 1933. Not applicable.

               (c)  Item 703 of Regulation S-K. Not applicable as the
                    Registrant has no class of equity securities registered
                    pursuant to section 12 of the Securities Exchange Act of
                    1934.

Item 6.        Selected Financial Data.

               Not applicable. See the Relief Letter.

Item 7.        Management's Discussion and Analysis of Financial Condition
               and Results of Operation.

               Not applicable. See the Relief Letter.

Item 7A        Quantitative and Qualitative Disclosures about Market Risk.

               Not applicable.

Item 8.        Financial Statements and Supplementary Data.

               Not applicable. See the Relief Letter.


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<PAGE>


Item 9.        Changes in and Disagreements With Accountants on Accounting
               and Financial Disclosure.

               None.

Item 9A.       Controls and Procedures.

               Not applicable. The Registrant is an Asset-Backed Issuer (as
               defined in Exchange Act Rule 15d-14(g)) and is therefore not
               required to disclose information under Item 307 of Regulation
               S-K. See Item 307 of Regulation S-K and Exchange Act Rule
               15d-15(a). The Registrant is an Asset-Backed Issuer (as defined
               in Exchange Act Rule 15d-14(g)) and is therefore not required
               to disclose information under Item 308 of Regulation S-K. See
               Instruction 2 to Item 308 of Regulation S-K and Exchange Act
               Rule 15d-15(a).

Item 9B.       Other Information.

               None.


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<PAGE>


                                   PART III

Item 10.       Directors and Executive Officers of the Registrant.

               Not applicable. See the Relief Letter.

Item 11.       Executive Compensation.

               Not applicable. See the Relief Letter.

Item 12.       Security Ownership of Certain Beneficial Owners and Management.

               Information required by Item 201(d) of Regulation S-K: Not
               applicable.

               Information required by Item 403 of Regulation S-K:

               (a)  Not applicable. See the Relief Letter.

               (b)  Not applicable. See the Relief Letter.

               (c)  Not applicable. See the Relief Letter.

Item 13.       Certain Relationships and Related Transactions.

               Not applicable. See the Relief Letter.

Item 14.       Principal Accounting Fees and Services.

               Not applicable. The Registrant is an Asset-Backed Issuer (as
               defined in Exchange Act Rule 15d-14(g)) and is therefore not
               required to disclose this information. See Instructions to Item
               14.


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<PAGE>


                                    PART IV

Item 15.       Exhibits and Financial Statement Schedules.

               (a)  (1)  Pursuant to the Pooling and Servicing Agreement,
                         the Master Servicer is required (i) to deliver an
                         annual statement as to compliance with the provisions
                         of the Pooling and Servicing Agreement and certain
                         other matters (the "Annual Statement of the Master
                         Servicer") and (ii) to cause a firm of independent
                         public accountants to deliver an annual report as to
                         compliance with the servicing provisions of the
                         Pooling and Servicing Agreement (the "Annual Report
                         of the Firm of Accountants"). The Annual Statement of
                         the Master Servicer is attached as Exhibit 99.1 to
                         this Report. The Annual Report of the Firm of
                         Accountants is attached as Exhibit 99.2 to this
                         Report. See Relief Letter.

                    (2)  Not applicable.

                    (3)  The required exhibits are as follows:

                         o    Exhibit 3(i): Copy of Company's Certificate of
                              Incorporation (Filed as an Exhibit to
                              Registration Statement on Form S-3 (File No.
                              33-63714)).

                         o    Exhibit 3(ii): Copy of Company's By-laws (Filed
                              as an Exhibit to Registration Statement on Form
                              S-3 (File No. 33-63714)).

                         o    Exhibit 4: Pooling and Servicing Agreement
                              (Filed as part of the Registrant's Current
                              Report on Form 8-K filed on August 23, 2004).

                         o    Exhibit 31: Rule 15d-14(a) Certification.

                         o    Exhibit 99.1: Annual Statement of the Master
                              Servicer.

                         o    Exhibit 99.2: Annual Report of the Firm of
                              Accountants.

               (b)  See subparagraph (a)(3) above.

               (c)  Not applicable. See the Relief Letter.


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<PAGE>


                                  SIGNATURES

     Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the Registrant has duly caused this Report to be signed
on its behalf by the undersigned, thereunto duly authorized.

                                  CWMBS, INC.,

                                  MORTGAGE PASS-THROUGH TRUST 2004-HYB4,
                                  MORTGAGE PASS-THROUGH CERTIFICATES,
                                  SERIES 2004-HYB4

                                By:  Countrywide Home Loans Servicing LP,
                                     as Master Servicer*

                                By:  Countrywide GP, Inc.


                                By:  /s/ Joseph M. Candelario
                                     --------------------------
                                     Name:  Joseph M. Candelario
                                     Title: First Vice President

                                Date:  March 28, 2005


----------------

*    This Report is being filed by the Master Servicer on behalf of the Trust
     Fund. The Trust Fund does not have any officers or directors.


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<PAGE>


     SUPPLEMENTAL INFORMATION TO BE FURNISHED WITH REPORTS FILED PURSUANT TO
SECTION 15(d) OF THE ACT BY REGISTRANTS WHICH HAVE NOT REGISTERED SECURITIES
PURSUANT TO SECTION 12 OF THE ACT.

     No such annual report, proxy statement, form of proxy or other soliciting
material has been, or will be, sent to Certificateholders. See the Relief
Letter.


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<PAGE>


                                 EXHIBIT INDEX

Exhibit      Document

3(i)         Company's Certificate of Incorporation (Filed as an Exhibit to
             Registration Statement on Form S-3 (File No. 33-63714))*

3(ii)        Company's By-laws (Filed as an Exhibit to Registration Statement
             on Form S-3 (File No. 33-63714))*

4            Pooling and Servicing Agreement (Filed as part of the Company's
             Current Report on Form 8-K filed on August 23, 2004)*

31           Rule 15d-14(a) Certification

99.1         Annual Statement of the Master Servicer

99.2         Annual Report of the Firm of Accountants

---------------------

*    Incorporated herein by reference.


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