EXHIBIT 8.1 [LETTERHEAD OF WARNER NORCROSS & JUDD LLP] April 27, 1999 Old Kent Financial Corporation CFSB Bancorp, Inc. 111 Lyon Street N.W. 112 Allegan Street Grand Rapids, Michigan 49503 Lansing, Michigan 48933 You have each requested our opinion regarding the federal income tax consequences of the proposed affiliation of CFSB Bancorp, Inc. ("CFSB") with Old Kent Financial Corporation ("Old Kent") through the proposed merger (the "Merger") of OKFC Acquisition Corporation ("MergerSub") into CFSB under the terms of an Agreement and Plan of Merger dated as of February 24, 1999 (the "Merger Agreement"), among Old Kent, MergerSub and CFSB, followed by the liquidation of CFSB. Capitalized terms not defined herein shall have the meanings ascribed to them in the Merger Agreement. MergerSub will be merged into CFSB under the laws of the states of Michigan and Delaware and in accordance with the Merger Agreement. In the Merger, all of the issued and outstanding shares of CFSB Common Stock will be converted into shares of Old Kent Common Stock. Immediately after the Merger, CFSB will be liquidated and dissolved, and all of its assets and liabilities will be transferred to and assumed by Old Kent. This opinion is based upon facts regarding the Merger as described in the Prospectus and Proxy Statement contained in the Registration Statement, and on the following assumptions: 1. The fair market value of the Old Kent Common Stock to be received by each CFSB stockholder will be approximately equal to the fair market value of the CFSB Common Stock surrendered in the exchange. 2. Old Kent has no plan or intention to reacquire any of the Old Kent Common Stock issued in the transaction, other than purchases of stock in the open market in the normal course of business executed through an independent broker in which Old Kent is not aware of the identity of any seller. Old Kent did not create and has not modified its stock repurchase program in connection with the acquisition of CFSB. WARNER NORCROSS & JUDD LLP Old Kent Financial Corporation CFSB Bancorp, Inc. April 27, 1999 Page 2 3. Old Kent will acquire at least 90% of the fair market value of the net assets and at least 70% of the fair market value of the gross assets held by CFSB immediately prior to the transaction. For purposes of this assumption, amounts paid by CFSB to dissenters, amounts used by CFSB to pay its reorganization expenses, amounts paid by CFSB to shareholders who receive cash or other property and all redemptions and distributions (except for regular, normal dividends) made by CFSB immediately preceding the transaction will be included as assets of CFSB held immediately prior to the transaction. 4. Old Kent will acquire solely for voting stock property of CFSB having a fair market value which is at least 80% of the fair market value of all of the property of CFSB. 5. Old Kent has formed MergerSub solely for the purpose of the acquisition transaction. MergerSub will not engage in any business other than as necessary incident to its merger into CFSB. 6. Immediately after the Merger, Old Kent will liquidate and dissolve CFSB as part of an overall plan for Old Kent to acquire the assets of CFSB. 7. Old Kent has no plan or intention to sell or otherwise dispose of any of the assets of CFSB acquired in the transaction, except for dispositions made in the ordinary course of business or transfers described in Section 368(a)(2)(C) of the Internal Revenue Code of 1986, as amended (the "Code"). 8. The liabilities of CFSB to be assumed by Old Kent and the liabilities to which the assets of CFSB to be transferred are subject were incurred by CFSB in the ordinary course of its business. 9. Following the transaction, Old Kent will continue the historic business of CFSB or use a significant portion of CFSB's historic business assets in a business. 10. Each of Old Kent, CFSB, and the stockholders of CFSB will pay their respective expenses, if any, incurred in connection with the transaction. WARNER NORCROSS & JUDD LLP Old Kent Financial Corporation CFSB Bancorp, Inc. April 27, 1999 Page 3 11. There is no intercorporate indebtedness existing between Old Kent and CFSB that was issued, acquired, or will be settled at a discount. 12. No party to the transaction is an investment company as defined in Section 368(a)(2)(F)(iii) and (iv) of the Code. 13. Old Kent does not own, nor has it owned during the past five years, any shares of the stock of CFSB. 14. On the date of the transaction, the fair market value of the assets of CFSB will exceed the sum of its liabilities, if any, to which the assets are subject. 15. CFSB is not under the jurisdiction of a court in a Title 11 or similar case within the meaning of Section 368(a)(3)(A) of the Code. 16. None of the compensation or other payments received by any stockholder-employees of CFSB will be separate consideration for or allocable to, any of their shares of CFSB Common Stock; none of the shares of Old Kent Common Stock received by any stockholder-employees of CFSB will be separate consideration for, or allocable to, any employment agreement; and the compensation paid to any stockholder- employees will be for services actually rendered and will be commensurate with amounts paid to third parties bargaining at arm's length for similar services. 17. The payment of cash to CFSB stockholders in lieu of fractional shares of Old Kent Common Stock will not be separately bargained for consideration, but will be undertaken solely for the purpose of avoiding the expense and inconvenience of issuing and transferring fractional shares. Based on the facts and assumptions set forth above, and subject to the limitations and conditions identified in this opinion, it is our opinion that the Merger of MergerSub into CFSB will be disregarded and the acquisition of the stock of CFSB and its liquidation by Old Kent will be WARNER NORCROSS & JUDD LLP Old Kent Financial Corporation CFSB Bancorp, Inc. April 27, 1999 Page 4 treated for federal income tax purposes as the acquisition by Old Kent of the substantially all of the assets of CFSB in exchange for Old Kent Common Stock and the assumption by Old Kent of the liabilities of CFSB followed by a distribution from CFSB to its stockholders of the Old Kent Common Stock in exchange for their CFSB stock in a transaction qualifying as a reorganization under Section 368(a)(1)(C) of the Code. CFSB and Old Kent will each be "a party to a reorganization" within the meaning of Section 368(b). In addition: 1. No gain or loss will be recognized by Old Kent upon the receipt by Old Kent of the assets of CFSB in exchange for the Old Kent Common Stock and the assumption by Old Kent of the liabilities of CFSB. 2. The basis of the assets of CFSB to be received by Old Kent will be the same as the basis of those assets in the hands of CFSB immediately prior to the Merger. 3. CFSB will not recognize any gain or loss on the transfer of its assets to Old Kent in exchange for Old Kent Common Stock. 4. The holding period of the assets of CFSB to be received by Old Kent will include the holding period of those assets in the hands of CFSB. 5. No gain or loss will be recognized by the stockholders of CFSB who receive shares of Old Kent Common Stock in exchange for all of their shares of CFSB Common Stock, except to the extent of any cash received in lieu of a fractional share of Old Kent Common Stock. 6. The basis of the Old Kent Common Stock (including fractional share interests) to be received by stockholders of CFSB will, in each instance, be the same as the basis of the respective shares of CFSB Common Stock surrendered in exchange therefor. 7. The holding period of the Old Kent Common Stock to be received by stockholders of CFSB will, in each instance, include the period during which the CFSB Common Stock surrendered in exchange therefor was held, provided that the CFSB Common Stock was, in each instance, held as a capital asset in the hands of the stockholders of CFSB at the date of the exchange. WARNER NORCROSS & JUDD LLP Old Kent Financial Corporation CFSB Bancorp, Inc. April 27, 1999 Page 5 We express no opinion about the tax treatment of the transaction under other provisions of the Code and regulations or about the tax treatment of any conditions existing at the time of, or the effects resulting from, the Merger that are not specifically covered above. We consent to the filing of this opinion as an exhibit to the Registration Statement and to the references to our firm in the Registration Statement. This opinion is rendered for the purposes of Item 21 of Form S-4 and Item 601 of Regulation S-K, may be relied upon only by you and the Commission and may not be used, quoted or referred to or filed for any other purpose without our prior written permission. WARNER NORCROSS & JUDD LLP By /S/ STEPHEN R. KRETSCHMAN Stephen R. Kretschman, a Partner