The third International Workshop on Collaborative Peer-to-Peer Information Systems, COPS07 was held in Paris INT as part of WETICE-2007. It was the third meeting devoted to the study of the field of Cooperative Information Systems and P2P networks or Cooperative P2P-based Information Systems (COPS). This year has emerged that COPS idea is becoming extremely diffuse among several areas of research and applications (Distributed systems, Real Time Information Systems, etc.). Also this year has been confirmed the importance of SOA architectures as unifying approach. Other important emerging issues are QoS for SOA architectures based on P2P systems and the role of SOA-based COPS in human-robots applications.