This book constitutes the thoroughly refereed post-workshop proceedings of the 7th International Workshop on Agents and Peer-to-Peer Computing, AP2PC 2008, held in Estoril, Portugal, in May 2008 and the 8th International Workshop on Agents and Peer-to-Peer Computing, AP2PC 2009, held in Budapest, Hungary, May 2009, co-located with the International Joint Conference on Autonomous Agents and Multi-Agent Systems, AAMAS. The 13 revised full papers presented were carefully reviewed and selected from numerous submissions. The volume is organized in topical sections on social welfare, distributed information sharing, and network organization and efficiency.