EXHIBIT 2.3


                SECOND AMENDMENT TO AGREEMENT AND PLAN OF MERGER

THIS SECOND AMENDMENT TO AGREEMENT AND PLAN OF MERGER is made and entered into
as of this 18th day of May, 1998 by and among (i) InSight Health Services Corp.,
a Delaware corporation ("InSight"), (ii)  SMSI Acquisition Company, a Delaware
corporation and a wholly-owned subsidiary of InSight ("Newco"), (iii) Signal
Medical Services, Inc., a Delaware corporation (the "Company"), (iv) SMSI
Holdings, Inc., a Connecticut corporation ("SMSI") and (v) Brian P. Stone
("Stone"), Thomas W. Crucitti ("Crucitti") and Todd Stowell ("Stowell") (Stone,
Crucitti and Stowell are sometimes collectively referred to herein as the
"Minority Stockholders" and, with SMSI, as the "Stockholders").

                                    RECITALS

     A.   InSight, Newco, the Company and the Stockholders are parties to an
Agreement and Plan of Merger dated as of April 15, 1998 (the "Agreement").

     B.   The parties wish to amend the Agreement to make the changes set forth
below.

     NOW THEREFORE, in consideration of the foregoing and the mutual promises
herein contained, InSight, Newco, the Company and the Stockholders mutually
agree as follows, with capitalized terms used herein and not defined having the
meanings ascribed to them in the Agreement:

     1.   References in Section 2.2(b) of the Agreement to (a) the Dollar amount
$25,519,936 are hereby changed to $24,970,120, and (b) the Dollar amount
$20,809,064 are hereby changed to $21,358,880.

     2.   References in Sections 7.2(f) and 8.2(d) of the Agreement to the
Dollar amount $6,160,064 are hereby changed to $6,709,880.

     3.   The reference in Section 7.8(a) of the Agreement to the Dollar amount
$4,945,941 is hereby changed to $5,371,123.

     4.   Except as amended hereby, the Agreement remains in full force and
effect and the parties hereby ratify and confirm each and every provision
thereof.



          [Remainder of Page Intentionally Left Blank; Signature Page Follows.]




     IN WITNESS WHEREOF, the parties have caused this Agreement to be fully 
executed and delivered, all as of the date and year first above written.

                                     INSIGHT HEALTH SERVICES CORP.
                              
                              
                                     By:  /S/  E. LARRY ATKINS 
                                          --------------------------------
                                          Name:   E. Larry Atkins
                                          Title:  President and CEO
                              
                                     SMSI ACQUISITION COMPANY
                              
                              
                                     By:  /S/ E. LARRY ATKINS
                                          ---------------------------------
                                          Name:   E. Larry Atkins
                                          Title:  President and CEO
                              
                                     SIGNAL MEDICAL SERVICES, INC.
                              
                              
                                     By:  /S/ BRIAN P. STONE
                                          ---------------------------------
                                          Name:   Brian P. Stone
                                          Title:  CEO
                              
                                     SMSI HOLDINGS, INC.
                              
                              
                                     By:  /S/ ROBERT T. BROWN  
                                          ---------------------------------
                                          Name:   Robert T. Brown
                                          Title:
                              
                                     MINORITY STOCKHOLDERS
                              
                                     /S/ BRIAN P. STONE
                                     ----------------------------
                                     Brian P. Stone
                              
                                     /S/ THOMAS W. CRUCITTI
                                     ----------------------------
                                     Thomas W. Crucitti
                              
                                     /S/ TODD STOWELL
                                     ----------------------------
                                     Todd Stowell