Embodiment of the present invention include a method, system and computer program product for a data processing system for QoS based planning in a Web services aggregation. The system can include Web service aggregation and coordination logic configured to identify accessible Web services in a registry and to arrange an aggregation of the Web services for invocation responsive to requests received from communicatively coupled clients over a computer communications network. The system further can include QoS planning logic coupled to the Web service aggregation and coordination logic. The QoS planning logic can be enabled to measure both the individual performance of the Web services in an aggregation of Web services and also the cumulative performance of the aggregation of Web services. Finally, the QoS planning logic can be enabled to modify the aggregation of Web services responsive to measuring both of the individual performance of Web services in the aggregation of Web services and also of the cumulative performance of the aggregation of Web services.