This volume constitutes the refereed proceedings of the Fourth European Conference, ServiceWave 2011, held in Poznan, Poland, in October 2011. The 25 revised full papers presented together with 3 invited presentations were carefully reviewed and selected from numerous submissions. They are organized in topical sections on cloud computing, security, privacy and trust, service engineering fundamentals, business services, and FI-PPP. In addition to the scientific track, 14 extended abstracts of demonstrations covering a wide spectrum of technology and application domains were accepted.