Exhibit 31.2



CERTIFICATION



I, Stephen A. Thorington, Executive Vice President and Chief Financial Officer of Plains Resources Inc., certify that:



|1. |  | I have reviewed this quarterly report on Form 10-Q of Plains Resources Inc.;
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|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;
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|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;
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|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)) [omitted in accordance with section III.E. of SEC Release No. 34-47986] for the registrant and we have:
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| | 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;
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| | b. |  | [omitted in accordance with section III.E. of SEC Release No. 34-47986];
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| | c. |  | 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
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| | d. |  | 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 (the
registrants fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrants control over financial reporting; and
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|5. |  | The registrants other certifying officer and I have disclosed, based on our most recent evaluation, to the registrants auditors and the audit committee of registrants board
of directors (or persons performing the equivalent function):
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| | a. |  | all significant deficiencies and material weaknesses in the design or operation of internal controls over financial reporting which are reasonably likely to adversely affect the
registrants ability to record, process, summarize and report financial information; and
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| | b. |  | any fraud, whether or not material, that involves management or other employees who have a significant role in the registrants internal controls over financial reporting.
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|Date: May 6, 2004 |  | /s/    Stephen A. Thorington                                                           
|                  |  |                                                                                        
|                  |  | Name: Stephen A. Thorington Title: Executive Vice President and Chief
Financial Officer