This book constitutes the refereed proceedings of the 4th COST Action 263 International Workshop on Quality of Future Internet Services, QoFIS 2003, held in Stockholm, Sweden in October 2003. The 22 revised full papers presented were carefully reviewed and selected from 73 submissions. The papers are organized in topical sections on performance analysis, quality of service provisioning, traffic engineering and routing, local area and multi-hop wireless networks, and cellular networks.