Exhibit 23.1 CONSENT OF INDEPENDENT ACCOUNTANTS We hereby consent to the incorporation by reference in the Registration Statements on Form S-8 (Nos. 333-13143, 333-13717, 333-53139, 333-55878, 333-76674, 333-88652 and 333-111283) of Millennium Chemicals Inc. of our report dated March 8, 2004 relating to the Equistar Chemicals, LP consolidated financial statements, which appears in this Annual Report on Form 10-K/A. PricewaterhouseCoopers LLP Houston, Texas April 26, 2004