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EXHIBIT 31 Certification of Chief Executive Officer
Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 I, James L. Fares, certify that: 1. I have reviewed this quarterly report on Form 10-Q of Questcor Pharmaceuticals, Inc.; 2. Based on my knowledge, this report does not contain any untrue statement of a material fact or
omit to state a material fact necessary to make the statements made, in light of the circumstances
under which such statements were made, not misleading with respect to the period covered by this
report; 3. Based on my knowledge, the financial statements, and other financial information included in
this report, fairly present in all material respects the financial condition, results of operations
and cash flows of the registrant as of, and for, the periods presented in this report; 4. The registrants other certifying officer and I are responsible for establishing and maintaining
disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for
the registrant and have: a) designed such disclosure controls and procedures, or caused such disclosure controls and
procedures to be designed under our supervision, to ensure that material information relating
to the registrant, including its consolidated subsidiaries, is made known to us by others
within those entities, particularly during the period in which this report is being prepared; b) evaluated the effectiveness of the registrants disclosure controls and procedures
and presented in this report our conclusions about the effectiveness of the disclosure
controls and procedures, as of the end of the period covered by this report based on such
evaluation; and c) disclosed in this report any change in the registrants internal control over
financial reporting that occurred during the registrants most recent fiscal quarter that has
materially affected, or is reasonably likely to materially affect, the registrants internal
control over financial reporting; and 5. The registrants other certifying officer and I have disclosed, based on our most recent
evaluation of internal control over financial reporting, to the registrants auditors and the audit
committee of the registrants board of directors (or persons performing the equivalent functions): a) all significant deficiencies and material weaknesses in the design or operation of
internal control over financial reporting which are reasonably likely to adversely affect the
registrants ability to record, process, summarize and report financial information; and b) any fraud, whether or not material, that involves management or other employees who
have a significant role in the registrants internal control over financial reporting. Date:
May 16, 2005 /s/  JAMES L. FARESJames L. FaresChief Executive Officer




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Certification of Principal Accounting Officer
Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 I, Barbara J. McKee, certify that: 1. I have reviewed this quarterly report on Form 10-Q of Questcor Pharmaceuticals, Inc.; 2. Based on my knowledge, this report does not contain any untrue statement of a material fact or
omit to state a material fact necessary to make the statements made, in light of the circumstances
under which such statements were made, not misleading with respect to the period covered by this
report; 3. Based on my knowledge, the financial statements, and other financial information included in
this report, fairly present in all material respects the financial condition, results of operations
and cash flows of the registrant as of, and for, the periods presented in this report; 4. The registrants other certifying officer and I are responsible for establishing and maintaining
disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for
the registrant and have: a) designed such disclosure controls and procedures, or caused such disclosure controls
and procedures to be designed under our supervision, to ensure that material information
relating to the registrant, including its consolidated subsidiaries, is made known to us by
others within those entities, particularly during the period in which this report is being
prepared; b) evaluated the effectiveness of the registrants disclosure controls and procedures and
presented in this report our conclusions about the effectiveness of the disclosure controls
and procedures, as of the end of the period covered by this report based on such
evaluation; and c) disclosed in this report any change in the registrants internal control over financial
reporting that occurred during the registrants most recent fiscal quarter that has
materially affected, or is reasonably likely to materially affect, the registrants
internal control over financial reporting; and 5. The registrants other certifying officer and I have disclosed, based on our most recent
evaluation of internal control over financial reporting, to the registrants auditors and the audit
committee of the registrants board of directors (or persons performing the equivalent functions): a) all significant deficiencies and material weaknesses in the design or operation of
internal control over financial reporting which are reasonably likely to adversely affect
the registrants ability to record, process, summarize and report financial information;
and b) any fraud, whether or not material, that involves management or other employees who
have a significant role in the registrants internal control over financial reporting. Date:
May 16, 2005 /s/ BARBARA J. MCKEEBarbara J. McKeePrincipal Accounting Officer