CUSIP No. 750491102

NAME OF REPORTING PERSONS

I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

    Red Mountain Capital Partners LLC

    73-1726370

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

(a)  x        (b)  ¨

SEC USE ONLY

SOURCE OF FUNDS*

    AF (See Item 3)

CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO

ITEMS 2(d) or 2(e)

CITIZENSHIP OR PLACE OF ORGANIZATION

    Delaware

NUMBER OF

SHARES

BENEFICIALLY

OWNED BY

EACH REPORTING

PERSON

WITH

SOLE VOTING POWER

    2,151,749 shares (See Item 5)

SHARED VOTING POWER

    None (See Item 5)

SOLE DISPOSITIVE POWER

    2,151,749 shares (See Item 5)

SHARED DISPOSITIVE POWER

    None (See Item 5)

11

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    2,151,749 shares (See Item 5)

12

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*

13

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    5.8% (See Item 5)

14.

TYPE OF REPORTING PERSON*

    OO – Limited Liability Company

CUSIP No. 750491102

NAME OF REPORTING PERSONS

I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

    Red Mountain Capital Partners II, L.P.

    20-4117535

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

(a)  x        (b)  ¨

SEC USE ONLY

SOURCE OF FUNDS*

    WC (See Item 3)

CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO

ITEMS 2(d) or 2(e)

CITIZENSHIP OR PLACE OF ORGANIZATION

    Delaware

NUMBER OF

SHARES

BENEFICIALLY

OWNED BY

EACH REPORTING

PERSON

WITH

SOLE VOTING POWER

    2,151,749 shares (See Item 5)

SHARED VOTING POWER

    None (See Item 5)

SOLE DISPOSITIVE POWER

    2,151,749 shares (See Item 5)

SHARED DISPOSITIVE POWER

    None (See Item 5)

11

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    2,151,749 shares (See Item 5)

12

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*

13

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    5.8% (See Item 5)

14.

TYPE OF REPORTING PERSON*

    PN – Limited Partnership

CUSIP No. 750491102

NAME OF REPORTING PERSONS

I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

    RMCP GP LLC

    20-4442412

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

(a)  x        (b)  ¨

SEC USE ONLY

SOURCE OF FUNDS*

    AF (See Item 3)

CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO

ITEMS 2(d) or 2(e)

CITIZENSHIP OR PLACE OF ORGANIZATION

    Delaware

NUMBER OF

SHARES

BENEFICIALLY

OWNED BY

EACH REPORTING

PERSON

WITH

SOLE VOTING POWER

    2,151,749 shares (See Item 5)

SHARED VOTING POWER

    None (See Item 5)

SOLE DISPOSITIVE POWER

    2,151,749 shares (See Item 5)

SHARED DISPOSITIVE POWER

    None (See Item 5)

11

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    2,151,749 shares (See Item 5)

12

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*

13

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    5.8% (See Item 5)

14.

TYPE OF REPORTING PERSON*

    OO – Limited Liability Company

CUSIP No. 750491102

NAME OF REPORTING PERSONS

I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

    Red Mountain Capital Management, Inc.

    13-4057186

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

(a)  ¨        (b)  x

SEC USE ONLY

SOURCE OF FUNDS*

    AF (See Item 3)

CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO

ITEMS 2(d) or 2(e)

CITIZENSHIP OR PLACE OF ORGANIZATION

    Delaware

NUMBER OF

SHARES

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

    2,151,749 shares (See Item 5)

SHARED VOTING POWER

    None (See Item 5)

SOLE DISPOSITIVE POWER

    2,151,749 shares (See Item 5)

SHARED DISPOSITIVE POWER

    None (See Item 5)

11

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    2,151,749 shares (See Item 5)

12

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*  

13

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    5.8% (See Item 5)

14.

TYPE OF REPORTING PERSON*

    CO – Corporation

CUSIP No. 750491102

NAME OF REPORTING PERSONS

I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

    Willem Mesdag

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

(a)  ¨        (b)  x

SEC USE ONLY

SOURCE OF FUNDS*

    AF (See Item 3)

CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO

ITEMS 2(d) or 2(e)

CITIZENSHIP OR PLACE OF ORGANIZATION

    U.S. Citizen

NUMBER OF

SHARES

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

    2,151,749 shares (See Item 5)

SHARED VOTING POWER

    None (See Item 5)

SOLE DISPOSITIVE POWER

    2,151,749 shares (See Item 5)

SHARED DISPOSITIVE POWER

    None (See Item 5)

11

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    2,151,749 shares (See Item 5)

12

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*

13

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    5.8% (See Item 5)

14.

TYPE OF REPORTING PERSON*

    IN – Individual

CUSIP No. 750491102

This Schedule 13D is being jointly filed by (i) Red Mountain Capital Partners LLC, a Delaware limited liability company (“RMCP LLC”), (ii) Red Mountain Capital Partners II, L.P., a Delaware limited partnership (“RMCP II”), (iii) RMCP GP LLC, a Delaware limited liability company (“RMCP GP”), (iv) Red Mountain Capital Management, Inc., a Delaware corporation (“RMCM”), and (v) Willem Mesdag, a natural person and citizen of the United States of America. RMCP LLC, RMCP II and RMCP GP are sometimes collectively referred to herein as “Red Mountain.” Red Mountain, RMCM and Mr. Mesdag are sometimes collectively referred to herein as the “Reporting Persons.”

The principal business of RMCP II is investment. RMCP II was not formed for the specific purpose of investing in the securities of RadNet.

RMCP GP is the general partner of RMCP II and thus may be deemed to control RMCP II. The principal business of RMCP GP is investment.

RMCP LLC is the managing member of RMCP GP and thus may be deemed to control RMCP GP and each entity directly or indirectly controlled by RMCP GP. The principal business of RMCP LLC is investment.

RMCM is the managing member of RMCP LLC and thus may be deemed to control RMCP LLC and each entity directly or indirectly controlled by RMCP LLC. The principal business of RMCM is investment.

Mr. Mesdag is the president, sole executive officer, sole director and sole shareholder of RMCM and thus may be deemed to control RMCM and each entity directly or indirectly controlled by RMCM (including Red Mountain). The principal occupation of Mr. Mesdag is Managing Partner of Red Mountain. He is a U.S. citizen.

Each of J. Christopher Teets and Mark Genender (and each of their principal occupation) is Partner of Red Mountain. Neither Mr. Teets nor Mr. Genender controls any Reporting Person. Information regarding Mr. Teets and Mr. Genender is being included in this Schedule 13D only for purposes of complying with General Instruction C to Schedule 13D. Each of them is a U.S. citizen.

The principal executive offices of RMCM and Red Mountain are located at, and the principal business address of Mr. Mesdag, Mr. Teets and Mr. Genender is, 10100 Santa Monica Boulevard, Suite 925, Los Angeles, California 90067.

During the last five years, none of the Reporting Persons, Mr. Teets or Mr. Genender has been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction as a result of which such person was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

CUSIP No. 750491102

RMCP II beneficially owns, in the aggregate, 2,151,749 shares of Common Stock, which represent approximately 5.8% of the outstanding Common Stock.⁽¹⁾ RMCP II has the sole power to vote or direct the vote, and the sole power to dispose or direct the disposition, of all such 2,151,749 shares of Common Stock.

Because each of RMCP GP, RMCP LLC, RMCM and Mr. Mesdag may be deemed to control RMCP II, each of RMCP GP, RMCP LLC, RMCM and Mr. Mesdag may be deemed to beneficially own, and to have the power to vote or direct the vote, or dispose or direct the disposition of, all of the Common Stock beneficially owned by RMCP II.

All calculations of percentage ownership in this Schedule 13D are based on 36,979,725 shares of Common Stock outstanding as of November 9, 2010, as reported in the Form 10-Q which was filed by RadNet with the Securities and Exchange Commission on November 9, 2010.

CUSIP No. 750491102

Other than shares of Common Stock beneficially owned by RMCP II, none of the Reporting Persons, Mr. Teets or Mr. Genender may be deemed to beneficially own any shares of Common Stock.

Each of RMCP LLC, RMCP II and RMCP GP affirms membership in a group with each other but disclaims membership in a group with RMCM or Mr. Mesdag. Each of RMCM and Mr. Mesdag disclaims membership in a group with any person.

The filing of this Schedule 13D shall not be construed as an admission that any Reporting Person is the beneficial owner of any of the shares of Common Stock that such Reporting Person may be deemed to beneficially own. Without limiting the foregoing sentence, each of RMCM and Mr. Mesdag disclaims beneficial ownership of all shares of Common Stock reported in this Schedule 13D. In addition, the filing of this Schedule 13D shall not be construed as an admission that any partner, member, director, officer or affiliate of any Reporting Person is the beneficial owner of any of the shares of Common Stock that such partner, member, director, officer or affiliate may be deemed to beneficially own. Without limiting the foregoing sentence, each of Mr. Teets and Mr. Genender disclaims beneficial ownership of all shares of Common Stock reported in this Schedule 13D.

The following table lists all transactions in Common Stock effected during the past sixty days by RMCP II. All such transactions were effected on the open market.

Shares of
Common
Stock
Purchased

Not applicable.

CUSIP No. 750491102

Exhibit
No.

Description of Exhibit

CUSIP No. 750491102

CUSIP No. 750491102

Exhibit
No.

Description of Exhibit