This book constitutes the refereed proceedings of the Third European Conference on Ambient Intelligence, AmI 2009, held in Salzburg, Austria, in November 2009. The 21 revised full papers and 10 short papers presented were carefully reviewed and selected from numerous submissions for inclusion in the book. The papers are organized in topical sections on sensing, reasoning and sensing, ambient technology, ambient assisted living, applications and studies, methods and tools, and reasoning and adaptation.