1 Exhibit 21.01 ONESOURCE INFORMATION SERVICES, INC. Subsidiaries of the Registrant Corporate Technology Information Services, Inc. 300 Baker Avenue Concord, MA 01742 Corporate Technology Information Services, Inc., incorporated under the laws of the state of Delaware, is a wholly-owned subsidiary of OneSource Information Services, Inc. OneSource Information Services Limited 7th Floor, Block E, Dukes Court Duke Street Woking, United Kingdom GU21 5BH OneSource Information Services Limited, incorporated under the laws of the United Kingdom, is a wholly-owned subsidiary of OneSource Information Services, Inc.