<PAGE>   1
                                                                    EXHIBIT 4(u)

                            STOCK PURCHASE AGREEMENT


         This Stock Purchase Agreement (this "Agreement") dated as of the 11th
day of January, 1999 between REGENT COMMUNICATIONS, INC., a Delaware corporation
(the "Company") and BLUE CHIP CAPITAL FUND II LIMITED PARTNERSHIP, an Ohio
limited partnership (the "Buyer").

         1. Authorization. The Company will authorize the sale and issuance
under this Agreement of 315,887 shares (the "Shares") of its Series G
Convertible Preferred Stock (the "Series G Preferred Stock"), having the rights,
privileges and preferences as set forth in the Certificate of Designation (the
"Certificate") in the form attached to this Agreement as Exhibit A. The shares
of Common Stock into which the Shares will be convertible are referred to herein
as the "Conversion Stock."

         2. Sale and Purchase of the Series G Preferred Stock. On and subject to
the terms and conditions set forth herein, the Company will sell, issue and
deliver to Buyer, and Buyer will purchase from the Company, 315,887 shares of
the Series G Convertible Preferred Stock.

         3. Closing Date. The closing of the purchase and sale of the Series G
Preferred Stock hereunder shall be on January 11, 1999 (the "Closing") or at
such other time upon which the Company and Buyer shall agree (the date of the
Closing is hereinafter referred to as the "Closing Date").

         4. Purchase Price. The purchase price for the Series G Preferred Stock
is One Million Five Hundred Seventy-Nine Thousand Four Hundred Thirty-Five
Dollars ($1,579,435.00) ($5.00 per share) (the "Purchase Price"), which sum
Buyer will pay to the Company by wire transfer of immediately available funds on
the Closing Date.

         5. Deliveries by the Company. At the Closing, the Company will deliver
to Buyer the following:

                  (a) a stock certificate or certificates representing the
Series G Preferred Stock duly issued in the name of Buyer and bearing the
legends set forth in Section 7(j) hereof; and

                  (b) an opinion of Strauss & Troy, as counsel to the Company,
in the form attached as Exhibit B.

         6. Representations and Warranties of the Company. The Company
represents and warrants to Buyer as follows:

                  (a) Organization and Qualification. The Company is a
corporation duly organized and existing under, and by virtue of, the laws of the
State of Delaware and is in good standing under such laws. The Company has
requisite power and authority to own and operate its properties and assets, and
to carry on its business as presently conducted. The Company is authorized to
transact business as a foreign corporation in good standing in those
jurisdictions in which the nature of its activities or the property owned by it
make such qualification necessary.

                  (b) Authorization. All corporate action on the part of the
Company necessary for the authorization, execution, delivery and performance of
this Agreement by the Company, the authorization, sale, issuance and delivery of
(i) the Shares and (ii) the Conversion Stock and the 

<PAGE>   2
performance of all of the Company's obligations hereunder has been taken or will
be taken prior to the Closing. This Agreement, when executed and delivered by
the Company, shall constitute the valid and binding obligation of the Company,
enforceable in accordance with its terms, except as enforcement may be limited
by bankruptcy, insolvency, reorganization, moratorium or similar laws affecting
enforcement of creditors' rights generally and except as enforcement is subject
to general principles of equity regardless of whether enforcement is considered
in a proceeding at law or in equity. The Shares, when issued in compliance with
the provisions of this Agreement, will be validly issued, fully paid and
nonassessable. The Conversion Stock has been duly and validly reserved and, when
issued in compliance with the provisions of this Agreement, will be validly
issued, fully paid and nonassessable. The Shares and the Conversion Stock will
be free of any liens or encumbrances, other than any liens or encumbrances
created by or imposed upon the holders thereof through no action of the Company;
provided, however, that the Shares and the Conversion Stock will be subject to
restrictions on transfer under state and/or federal securities laws as set forth
herein and under certain other restrictions as set forth in that certain Second
Amended and Restated Stockholders' Agreement dated as of June 15, 1998 among the
Company, Waller-Sutton Media Partners, L.P. et al. The issuance of the Shares
will not violate any preemptive rights available to the holders of any of the
Company's securities. The Series G Preferred Stock shall have the rights,
preferences, privileges and restrictions set forth in the Certificate.

                  (c) Compliance with Laws. The Company is not in violation of
(i) any applicable order, judgment, injunction, award or decree, or (ii) any
federal, state, local or foreign law, statute, rule, ordinance or regulation or
any other requirement of any governmental or regulatory body, court or
arbitrator applicable to the business of the Company except for violations which
reasonably could not have a material adverse effect on the business or
properties of the Company. The Company has obtained all licenses, permits,
orders and approvals of any federal, state, local or foreign governmental
regulatory body (collectively, "Permits") that are material to or necessary for
the conduct of the business of the Company. All of such Permits are in full
force and effect, no violations are or have been recorded in respect of any
Permit and no proceeding is pending or, to the best of the Company's knowledge,
threatened to revoke or limit any such Permit.

                  (d) Compliance with Other Instruments, None Burdensome, etc.
Except as set forth on Schedule 1 hereto, the Company is not in violation of any
term of its Amended and Restated Certificate of Incorporation or By-Laws, or, of
any term or provision of any material mortgage, indebtedness, indenture,
contract, agreement, instrument, judgment or decree. The execution, delivery and
performance of and compliance with this Agreement and the issuance of the Series
G Preferred Stock and the Conversion Stock have not resulted and will not result
in any violation of, or conflict with, or constitute a default under, the
Company's existing Amended and Restated Certificate of Incorporation or By-Laws
or any of its agreements or result in the creation of, any mortgage, pledge,
lien, encumbrance or charge upon any of the properties or assets of the Company.

                  (e) Litigation. Except as set forth on Schedule 1 hereto,
there are no actions, suits, proceedings or investigations pending against the
Company or its properties before any court or governmental agency (nor, to the
best of the Company's knowledge, is there any reasonable basis therefor or
threat thereof).

                  (f) Governmental Consent, etc. No consent, approval or
authorization of (or designation, declaration of filing with) any governmental
authority on the part of the Company is required in connection with the valid
execution and delivery of this Agreement, or the offer, sale or 


<PAGE>   3
issuance of the Series G Preferred Stock and the Conversion Stock, or the
consummation of any other transaction contemplated hereby, except (i) filing of
the Certificate in the office of the Secretary of State of the State of
Delaware, and (ii) qualification (or taking such action as may be necessary to
secure an exemption from qualification, if available) of the offer and sale of
the Series G Preferred Stock and the Conversion Stock under applicable state
securities laws, which filings and qualifications, if required, will be
accomplished in a timely manner.

                  (g) Offering. Subject to the accuracy of the Buyer's
representations in Section 7 hereof, the offer, sale and issuance of the Series
G Preferred Stock to be issued in conformity with the terms of this Agreement,
and the issuance of the Conversion Stock upon conversion of the Series G
Preferred Stock, constitute transactions exempt from the registration
requirements of Section 5 of the Securities Act of 1933, as amended (the
"Securities Act").

                  (h) Brokers or Finders. The Company has not incurred, and will
not incur, directly or indirectly, as a result of any action taken by the
Company, any liability for brokerage or finders' fees or agents' commissions or
any similar charges in connection with this Agreement.

                  (i) Disclosure. No representations or warranty by the Company
in this Agreement, nor any statement, document, or certificate, furnished or to
be furnished, to the Buyer in connection herewith, or pursuant hereto, contains
or will contain any untrue statement of a material fact, or omits or will omit
to state any material fact necessary to make any statement herein or therein not
misleading.

                  (j) No Material Adverse Change. Except as set forth on
Schedule 1 hereto and except for the utilization of available working capital in
the fourth quarter, between the date of the financial statements filed as part
of the Company's third quarter 10-Q and the Closing Date, there has not been any
change in the assets, liabilities, financial condition or operations of the
Company from that reflected in the financial statements, except changes in the
ordinary course of business which have not been, either in any case or in the
aggregate, materially adverse.

         7. Representations and Warranties of Buyer. Buyer hereby represents and
warrants to the Company with respect to the purchase of the Shares as follows:

                  (a) Non-Registration. Buyer understands that the offering and
sale of the Series G Preferred Stock is intended to be exempt from registration
under the Securities Act of 1933, as amended (the "1933 Act"), by virtue of
Section 4(2) of the Act and the provisions of Regulation D promulgated
thereunder, that the Series G Preferred Stock has not been registered under the
1933 Act or under the securities laws of any state, and that the Company will be
under no obligation to effect any such registration.

                  (b) Investment Intent. Buyer is purchasing the Series G
Preferred Stock and the Conversion Stock for its own account, for investment and
not with a view to resale, distribution, or other disposition, and Buyer has no
present plans to enter into any contract, undertaking, agreement or arrangement
for any such resale, distribution or other disposition. It understands that the
Shares and the Conversion Stock have not been, and will not be, registered under
the Securities Act by reason of a specific exemption from the registration
provisions of the Securities Act, the availability of which depends upon, among
other things, the bona fide nature of the investment intent and the accuracy of
such Buyer's representations as expressed herein. Buyer will not sell or
otherwise transfer the Series G 

<PAGE>   4
Preferred Stock without registration under the 1933 Act and applicable state
securities laws, or pursuant to an exemption from the registration requirements
thereof which, in the opinion of counsel reasonably acceptable to the Company,
is available for the transaction.

                  (c) Rule 144. Buyer acknowledges that the Shares and the
Conversion Stock must be held indefinitely unless subsequently registered under
the Securities Act or unless an exemption from such registration is available.
It is aware of the provisions of Rule 144 promulgated under the Securities Act
which permit limited resale of shares purchased in a private placement subject
to the satisfaction of certain conditions, including, among other things, the
existence of a public market for the shares, the availability of certain current
public information about the Company, the resale occurring not less than one
year after a party has purchased and paid for the security to be sold, the sale
being effected through a "broker's transaction" or in transactions directly with
a "market maker" and the number of shares being sold during any three-month
period not exceeding specified limitations.

                  (d) No Public Market. Buyer understands that no public market
now exists for the Shares and that the Company has made no assurances that a
public market will ever exist for the Shares.

                  (e) Status of Buyer. Buyer: (i) is an "accredited investor,"
as that term is defined in Rule 501(a) of Regulation D promulgated under the
1933 Act, inasmuch as Buyer meets the requirements of subparagraph (a)(3) of
Rule 501; (ii) was not formed for the primary purpose of evading federal or
state securities laws, and (iii) is a "Qualified Institutional Buyer" as defined
in 17 CFR .144A(a).

                  (f) Opportunity to Review Books and Records. Buyer has had a
reasonable opportunity to inspect all documents, books and records pertaining to
the Company and the Series G Preferred Stock and confirms that the Series G
Preferred Stock is being purchased without Buyer's receipt of any offering
literature.

                  (g) Opportunity for Questions. Buyer has had a reasonable
opportunity to ask questions of and receive answers from a person or persons
acting on behalf of the Company concerning the Company, its business and
operations, the terms of the Series G Preferred Stock and all other aspects of
investment in the Company, and all such questions have been answered to the full
satisfaction of Buyer.

                  (h) Manner of Purchase. Buyer is not subscribing for the
Series G Preferred Stock as a result of or pursuant to any advertisement,
article, notice or other communication published in any newspaper, magazine, or
similar media or broadcast over television or radio, or presented at any seminar
or meeting, or any solicitation of a subscription by a person other than a
representative of the Company.

                  (i) Brokers or Finders. Buyer has not incurred, and will not
incur, directly or indirectly, as a result of any action taken by the Company,
any liability for brokerage or finders' fees or agents' commissions or any
similar charges in connection with this Agreement.

                  (j) Legends. Buyer understands that the certificate(s)
representing the Series G Preferred Stock shall bear legends in substantially
the following forms, and Buyer shall not transfer any 


<PAGE>   5
of the shares of Series G Preferred Stock, or any shares of common stock that
may be issued on conversion thereof, or any interest therein, except in
accordance with the terms of such legends:

         "The securities represented by this certificate have not been
         registered under the Securities Act of 1933, as amended, or the
         securities laws of any state (the "Securities Laws"). These securities
         may not be offered, sold, transferred, pledged or hypothecated in the
         absence of registration under applicable Securities Laws, or the
         availability of an exemption therefrom. This certificate will not be
         transferred on the books of the Corporation or any transfer agent
         acting on behalf of the Corporation except upon the receipt of an
         opinion of counsel, satisfactory to the Corporation, that the proposed
         transfer is exempt from the registration requirements of all applicable
         Securities Laws, or the receipt of evidence, satisfactory to the
         Corporation, that the proposed transfer is the subject of an effective
         registration statement under all applicable Securities Laws."

         "The issuer is subject to restrictions contained in the Federal
         Communications Act, as amended. The securities evidenced by this
         certificate may not be sold, transferred, assigned or hypothecated if,
         as a result thereof, the issuer would be in violation of that act."

         "The securities represented by this certificate are subject to the
         terms and entitled to the benefits of that certain Registration Rights
         Agreement dated as of June 15, 1998 among the Company and certain of
         its stockholders, as the same may be amended from time to time, and
         that certain Second Amended and Restated Stockholders' Agreement dated
         as of June 15, 1998 among the Company and certain of its stockholders,
         as the same may be amended from time to time."

                  (k) Authority of Buyer. This Agreement, when executed and
delivered by the Buyer will constitute the legal, valid and binding obligation
of Buyer, enforceable against Buyer in accordance with its terms, except as
enforcement may be limited by bankruptcy, insolvency, reorganization, moratorium
or similar laws affecting enforcement of creditors' rights generally and except
as enforcement is subject to general principles of equity regardless of whether
enforcement is considered in a proceeding at law or in equity.

                  (l) No Conflicts. The execution, delivery and performance of
this Agreement by Buyer will not violate in any material respect any provision
of law or any rule or regulation of any federal, state or local governmental
authority to which Buyer is subject, nor result in a breach or violation by
Buyer of any of the terms or provisions of, or constitute an event of default
under, any material indenture, mortgage, trust (constructive or otherwise), loan
agreement, lease or other agreement or instrument to which Buyer is a party or
by which Buyer or its assets are bound. Buyer is not a party to, or subject to,
or bound by, any judgment, award, injunction, order or decree of any court or
governmental authority, or any arbitration award which may restrict or interfere
with the performance by Buyer of this Agreement or such other documents as may
be delivered by Buyer in connection herewith.

                  (m) Legal Proceedings. There is no action, suit, proceeding or
investigation pending (or, to the knowledge of Buyer, threatened) against Buyer
in, before or by any court, administrative 

<PAGE>   6
agency or arbitrator affecting the ability of Buyer to carry out the provisions
of this Agreement and the transactions contemplated hereby.

         8. Buyer's Conditions to Closing. The Buyer's obligation to purchase
the Shares at the Closing is subject to the fulfillment of the following
conditions:

                  (a) Representations and Warranties Correct. The
representations and warranties made by the Company in Section 6 hereof shall be
true and correct, if limited by materiality, in accordance with the terms
thereof in all respects, and if not so limited by materiality, in all material
respects, as of the Closing Date.

                  (b) Covenants. All covenants, agreements and conditions
contained in this Agreement to be performed by the Company on or prior to the
Closing Date shall have been performed or complied with in all material
respects.

                  (c) Compliance with State Securities Laws. The Company shall
have obtained all permits and qualifications required by any state for the offer
and sale of the Shares and the Conversion Stock, or shall have the availability
of exemptions therefrom.

                  (d) Legal Matters. All material matters of a legal nature
which pertain to this Agreement and the transactions contemplated hereby shall
have been reasonably approved by counsel to Buyer.

         9. Company's Conditions to Closing. The Company's obligation to sell
and issue the Shares at the Closing Date is, at the option of the Company,
subject to the fulfillment as of the Closing Date of the following conditions:

                  (a) Representations and Warranties Correct. The
representations and warranties made by Buyer in Section 7 hereof shall be true
and correct when made, and shall be true and correct on the Closing Date.

                  (b) Compliance with State Securities Laws. The Company shall
have obtained all permits and qualifications required by any state for the offer
and sale of the Shares and the Conversion Stock, or shall have the availability
of exemptions therefrom.

                  (c) Legal Matters. All material matters of a legal nature
which pertain to this Agreement, and the transactions contemplated hereby, shall
have been reasonably approved by counsel to the Company.

         10. Reimbursement of Legal Fees. The Company hereby agrees to reimburse
Buyer for its legal fees incurred in connection with the negotiation, execution
and performance of this Agreement.


<PAGE>   7
         11.      Miscellaneous.

                  (a) Notices. Any notice, request or other document to be given
hereunder to any party shall be effective upon receipt (or refusal of receipt)
and shall be in writing and delivered personally or sent by telecopy or
certified or registered mail, postage prepaid:

         (i)    if to the Company, addressed to:

                        Regent Communications, Inc.
                        50 East RiverCenter Boulevard, Suite 180
                        Covington, KY 41011
                        Attn: Terry S. Jacobs, Chairman of the Board
                        Facsimile: (606) 292-0352

                with a copy to:

                        Strauss & Troy
                        2100 PNC Center
                        201 East Fifth Street
                        Cincinnati, Ohio 45202
                        Attn:  Alan C. Rosser, Esq.
                        Facsimile:   (513) 241-8289

         (ii) if to Buyer, addressed to:

                        Blue Chip Capital Fund II Limited Partnership
                        250 East Fifth Street, Suite 1100
                        Cincinnati, Ohio 45202
                        Attn: John H. Wyant
                        Facsimile: (404) 723-2306



<PAGE>   8
         with copies to:

                 Taft, Stettinius & Hollister LLP
                 1800 Star Bank Center
                 425 Walnut Street
                 Cincinnati, Ohio 45202
                 Attn: Gerald S. Greenberg, Esq.
                 Facsimile:   (513) 381-0205

or to such other address or telecopy number as any party shall have specified by
notice given to the other parties in the manner specified above.

                  (b) Entire Agreement; Amendment. This Agreement, including the
Exhibits and Schedules hereto, and the other agreements expressly contemplated
by this Agreement, contain the entire agreement between the parties with respect
to the subject matter hereof and supersede all prior oral and written
agreements, memoranda, term sheets, understandings and undertakings among the
parties hereto relating to the subject matter hereof. This Agreement may be
modified or amended only by a written instrument executed by or on behalf of the
parties hereto.

                  (c) Governing Law. This Agreement shall be governed by, and
construed in accordance with, the internal laws of the State of Ohio without
regard to the application of its conflicts of laws principles. The parties
hereby waive all right to trial by jury in any action, suit or proceeding
brought to enforce or defend any rights or remedies under this Agreement or the
transactions contemplated hereby.

                  (d) Severability. In case any provision in this Agreement
shall be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions hereof shall not in any way be
affected or impaired thereby.

                  (e) Construction. The section and subsection headings used
herein are for convenience of reference only, are not a part of this Agreement
and are not to affect the construction of, or be taken into consideration in
interpreting, any provision of this Agreement. As used in this Agreement, the
masculine, feminine and neuter gender each includes the other, unless the
context otherwise dictates. Any and all schedules and exhibits referred to in
this Agreement and attached hereto are and shall be deemed to be incorporated in
this Agreement as if fully set forth herein.

                  (f) Counterparts. This Agreement may be executed in two or
more counterparts, each of which shall be deemed to be an original, but all of
which together shall constitute one and the same instrument.

                  (g) Specific Performance. The parties hereto acknowledge that
damages may be an inadequate remedy for any breach of the provisions of this
Agreement and agree that the obligations of the parties hereunder may be
specifically enforceable, and no party will take any action to impede the other
from seeking to enforce such right of specific performance after any such
breach.

                  (h) Successors and Assigns: Assignability. Except as otherwise
provided herein, this Agreement shall be binding upon and inure to the benefit
of and be enforceable by the parties hereto

<PAGE>   9
and their respective successors and permitted assigns; provided, however, that
the right of the Buyer to purchase the Series G Preferred Stock shall not be
assignable without the consent of the Company. This Agreement (i) shall not
confer upon any person other than the parties hereto and their respective
successors and permitted assigns any rights or remedies hereunder; and (ii)
shall not be assignable by either party without the prior written consent of the
other.

                  (i) Further Assurances. Subject to the terms and conditions
herein provided, each of the parties hereto agrees to use all reasonable efforts
to take, or cause to be taken, all action and to do, or cause to be done, all
things necessary proper or advisable to consummate and make effective the
transactions contemplated by this Agreement.

                  (j) Survival. The representations and warranties of the
parties contained herein shall survive execution and delivery of this Agreement
and issuance and delivery of the Series G Preferred Stock hereunder.


         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed and delivered, as of the day and year first above written.

               COMPANY:

               REGENT COMMUNICATIONS, INC.


               By: /s/                                                          

                Its: /s/                                                        



               BUYER:

               BLUE CHIP CAPITAL FUND II LIMITED PARTNERSHIP


               By: Blue Chip Venture Company, Ltd., its general partner

               By: /s/                                                          


               Its: /s/