Exhibit 23 CONSENT OF INDEPENDENT ACCOUNTANTS We hereby consent to the incorporation by reference in the Registration Statement on Form S-8 (No. 33-26867) of Lyondell Chemical Company of our report dated June 28, 1999 relating to the financial statements of the Lyondell Chemical Company 401(k) and Savings Plan, which appears in this Form 11-K. PricewaterhouseCoopers LLP Houston, Texas June 29, 1999 16