This book constitutes the refereed proceedings of the Third Hellenic Conference on Artificial Intelligence, SETN 2004, held at Samos, Greece in May 2004.

The 54 revised full papers presented together with 2 invited contributions were carefully reviewed and selected from numerous submissions. The papers are organized in topical sections on information management, machine learning, data mining and diagnostics, knowledge representation and search, natural language processing, AI in power systems operation and fault diagnosis, intelligent techniques in image processing, and intelligent virtual environments.