As Service-oriented Architectures (SOA) mature, an efficient approach for the integration of Web services in portals is required. This holds true especially in medium and large-scale SOA-based systems with a multitude of Web services to be made accessible to the users. The integration scenarios, i.e. the Web service-based features within a portal, are usually composed of complex sequences of user interaction and service communication, aggravating the need for an efficient integration solution. We present an approach for the business process-driven modeling of these scenarios in form of ?user interaction (UI) workflows? as well as a technical framework enabling the model execution within existing portal systems. The integration of Web services in a portal can thus be realized very efficiently by modeling UI workflows and configuring highly generic activity building blocks for dialog construction, service communication and data presentation.