Financial Derivatives Supervisory Improvement Act of 1998

Financial Derivatives Supervisory Improvement Act of 1998 - Establishes the Working Group on Financial Derivatives to study and report to the Congress on: (1) the regulation of derivatives markets in which domestic and foreign depository institutions and registered brokers and dealers participate; and (2) any recommendations for modernizing and harmonizing statutes, regulations, and policies.

Urges the Group to assign a high priority to continual negotiations to ensure that foreign markets and regulatory bodies establish and maintain regulations comparably prudent to those governing the U.S. markets.

Prohibits the Commodity Futures Trading Commission, for a specified time period, without the Secretary of the Treasury's approval, from promulgating or proposing regulations, or issuing any interpretive or policy statements that regulate or restrict activity in certain hybrid instruments and swap agreements. Declares that any such hybrid instruments or swap agreements entered into before such period shall not be subject to the Commodity Exchange Act's restriction of futures contracts or exempted securities.