<PAGE>


                                                                    Exhibit 31.2

                    CERTIFICATION PURSUANT TO SECTION 302 OF
                         THE SARBANES-OXLEY ACT OF 2002


I, John E. Lushefski, Executive Vice President and Chief Financial Officer of
Millennium Chemicals Inc., certify that:

     1.   I have reviewed the annual report on Form 10-K of Millennium Chemicals
          Inc. as filed with the Securities and Exchange Commission on March 25,
          2003 and as amended by Form 10-K/A filed with the Securities and
          Exchange Commission on the date hereof;

     2.   Based on my knowledge, this annual 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 annual report;

     3.   Based on my knowledge, the financial statements, and other financial
          information included in this annual 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 annual 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 annual 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 (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 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: November 12, 2003

                                                   /s/ JOHN E. LUSHEFSKI
                                               ---------------------------------
                                                      John E. Lushefski
                                                Executive Vice President and
                                                   Chief Financial Officer
                                                (Principal Financial Officer)