<PAGE>


                                                                Exhibit 99.1 (b)

(b) (I) PRO FORMA FINANCIAL INFORMATION

                 INSIGHT HEALTH SERVICES CORP. AND SUBSIDIARIES
              UNAUDITED PRO FORMA COMBINED CONDENSED BALANCE SHEET
                                 MARCH 31, 2000
                             (Amounts in thousands)

<TABLE>
<CAPTION>
                                                                                                 WILKES-BARRE      PRO
                                                                  HISTORICAL     HISTORICAL       ACQUISITION     FORMA
                                                                   INSIGHT      WILKES-BARRE      ADJUSTMENTS    COMBINED
                                                                  ----------    ------------     ------------    --------
<S>                                                               <C>            <C>            <C>             <C>
ASSETS
Current assets:
   Cash and cash equivalents                                      $  13,968      $     423      $    (423)(1)   $  13,968
   Trade accounts receivables, net                                   44,234          2,023         (2,023)(1)      44,234
   Other current assets                                               7,968             56           --             8,024
                                                                  ---------      ---------      ---------       ---------
     Total current assets                                            66,170          2,502         (2,446)         66,226
Property and equipment, net                                         138,494          5,859           (347)(1)     144,006
Investments in partnerships                                           1,505           --             --             1,505
Other assets                                                          7,838           --             --             7,838
Intangible assets, net                                               83,256           --           12,043(1)       95,299
                                                                  ---------      ---------      ---------       ---------
                                                                  $ 297,263      $   8,361      $   9,250       $ 314,874
                                                                  ---------      ---------      ---------       ---------
                                                                  ---------      ---------      ---------       ---------

LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
   Current portion of equipment, capital leases and other notes   $  21,764      $     757      $   1,797(1)    $  24,318
   Accounts payable and other accrued expenses                       21,955            708           (702)(1)      21,961
                                                                  ---------      ---------      ---------       ---------
    Total current liabilities                                        43,719          1,465          1,095          46,279
Equipment, capital leases and other notes, less current portion     203,590          5,059          9,992(1)      218,641
Other long-term liabilities                                           1,047           --             --             1,047
Stockholders' equity (deficit)                                       48,907          1,837         (1,837)(1)      48,907
                                                                  ---------      ---------      ---------       ---------
                                                                  $ 297,263      $   8,361      $   9,250       $ 314,874
                                                                  ---------      ---------      ---------       ---------
                                                                  ---------      ---------      ---------       ---------
</TABLE>

The pro forma condensed combined balance sheet as of March 31, 2000 reflects the
following pro forma adjustments:

(1) To record the acquisition of assets of Wilkes-Barre for $17,610 and the
resulting goodwill of $12,043.

The above reflects the acquisition of Wilkes-Barre by InSight using the purchase
method of accounting. Under the principles of purchase accounting, the assets
and liabilities of Wilkes-Barre are stated at fair market value (FMV). The
excess purchase price is allocated to goodwill.



                                       21
<PAGE>

    (b) (ii)
                 INSIGHT HEALTH SERVICES CORP. AND SUBSIDIARIES
           UNAUDITED PRO FORMA COMBINED CONDENSED STATEMENT OF INCOME
                        FOR THE YEAR ENDED JUNE 30, 1999
                  (AMOUNTS IN THOUSANDS, EXCEPT PER SHARE DATA)

<TABLE>
<CAPTION>
                                                                                       WILKES-BARRE             PRO
                                                        HISTORICAL       HISTORICAL     ACQUISITION            FORMA
                                                          INSIGHT       WILKES-BARRE    ADJUSTMENTS          COMBINED
                                                          -------       ------------    -----------          --------
<S>                                                        <C>               <C>                 <C>           <C>
 Revenues                                                  $ 161,992         $ 6,349             $ -           $ 168,341

 Costs of operations:
     Costs of services                                        85,317           2,990            (107)(3)          88,200
     Provision for doubtful accounts                           2,618             237               -               2,855
     Equipment leases                                         18,522               -               -              18,522
     Depreciation and amortization                            24,468             521             591  (1)         25,213
                                                                  -               -             (367) (2)             -
                                                            --------          ------            -----            -------
       Total costs of operations                             130,925           3,748             117             134,790
                                                            --------          ------            -----            -------
     Gross profit                                             31,067           2,601            (117)             33,551

 Corporate operating expenses                                 10,893               -               -              10,893

 Provision for reorganization and other costs                  3,300               -               -               3,300
                                                            --------          ------            -----           --------
     Income from company operations                           16,874           2,601            (117)             19,358

 Equity in earnings of unconsolidated partnerships               548               -               -                 548
                                                            --------          ------            -----           -------
     Operating income                                         17,422           2,601            (117)             19,906

 Interest expense, net                                        14,500             336           1,088   (4)        15,924
                                                            --------          ------           ------            -------
     Income before income taxes                                2,922           2,265          (1,205)              3,982

 Provision (benefit) for income taxes                         (3,190)             -              170   (5)        (3,020)
                                                            --------          ------          ------              -------
     Net income                                             $ 6,112         $ 2,265         $ (1,375)            $ 7,002
                                                            --------          ------        ---------            -------
                                                            --------          ------        ---------            -------
 Income per common and converted preferred share:
     Basic                                                   $ 0.67                                              $ 0.76
                                                            --------                                            -------
                                                            --------                                            -------
     Diluted                                                 $ 0.65                                              $ 0.75
                                                            --------                                            -------
                                                            --------                                            -------

 Weighted average number of common and preferred
   shares outstanding:
     Basic                                                    9,158                                               9,158
                                                            --------                                            -------
                                                            --------                                            -------
     Diluted                                                  9,376                                               9,376
                                                            --------                                            -------
                                                            --------                                            -------
</TABLE>

The pro forma combined condensed statement of income for the year ended June 30,
1999 reflects the following pro forma adjustments:

(1)  To record amortization of goodwill over 20 years.

(2)  To record depreciation expense on the estimated fair market value of assets
     acquired.

(3)  To reverse management fees charged by USD of $413 and record management
     fees charged by InSight of $306.

(4)  To record interest expense for acquisition financing.

(5)  To record the tax effect on the above entries at estimated effective rates.

                                       22
<PAGE>

(b) (iii)
                 INSIGHT HEALTH SERVICES CORP. AND SUBSIDIARIES
           UNAUDITED PRO FORMA COMBINED CONDENSED STATEMENT OF INCOME
                    FOR THE NINE MONTHS ENDED MARCH 31, 2000
                  (Amounts in thousands, except per share data)
<TABLE>
<CAPTION>
                                                                                                WILKES-BARRE     PRO
                                                                     HISTORICAL   HISTORICAL    ACQUISITION     FORMA
                                                                       INSIGHT   WILKES-BARRE   ADJUSTMENTS    COMBINED
                                                                       -------   ------------   -----------    --------
<S>                                                                   <C>        <C>            <C>            <C>
Revenues                                                              $139,977   $  6,554       $   --         $146,531

Costs of operations:
    Costs of services                                                   75,663      2,863           (122)(3)     78,404
    Provision for doubtful accounts                                      2,109        262           --            2,371
    Equipment leases                                                    11,297       --             --           11,297
    Depreciation and amortization                                       24,256        726            444         25,151
                                                                          --         --             (275)(2)       --
                                                                      --------   --------       --------       --------
      Total costs of operations                                        113,325      3,851             47        117,223
                                                                      --------   --------       --------       --------

    Gross profit                                                        26,652      2,703            (47)        29,308

Corporate operating expenses                                             8,215       --             --            8,215
                                                                      --------   --------       --------       --------
    Income from company operations                                      18,437      2,703            (47)        21,093

Equity in earnings of unconsolidated partnerships                          624       --             --              624
                                                                      --------   --------       --------       --------
    Operating income                                                    19,061      2,703            (47)        21,717

Interest expense, net                                                   13,548        478            622(4)      14,648
                                                                      --------   --------       --------       --------
    Income before income taxes                                           5,513      2,225           (669)         7,069

Provision for income taxes                                                 881       --              249(5)       1,130
                                                                      --------   --------       --------       --------

    Net income                                                        $  4,632   $  2,225       $   (918)      $  5,939
                                                                      --------   --------       --------       --------
                                                                      --------   --------       --------       --------

Income per common and converted preferred share:
    Basic                                                             $   0.50                                 $   0.64
                                                                      --------                                 --------
                                                                      --------                                 --------

    Diluted                                                           $   0.49                                 $   0.63
                                                                      --------                                 --------
                                                                      --------                                 --------

Weighted average number of common and preferred shares outstanding:
    Basic                                                                9,245                                    9,245
                                                                      --------                                 --------
                                                                      --------                                 --------
    Diluted                                                              9,383                                    9,383
                                                                      --------                                 --------
                                                                      --------                                 --------
</TABLE>

 The pro forma combined condensed statement of income for the nine months ended
     March 31, 2000 reflects the following pro forma adjustments:

(1)  To record amortization of goodwill over 20 years.

(2)  To record depreciation expense on the estimated fair market value of assets
     acquired.

(3)  To reverse management fees charged by USD of $436 and record management
     fees charged by InSight of $315.

(4)  To record interest expense for acquisition financing.

(5)  To record the tax effect on the above entries at estimated effective rates.

                                       23