This book constitutes the thoroughly refereed post-proceedings of the First International Conference on Digital Libraries, DELOS 2007, held in Pisa, Italy, in February 2007. The 33 revised full papers presented were carefully reviewed and selected for inclusion in the book. The papers are organized in topical sections on similarity search, architectures, personalization, interoperability, evaluation, miscellaneous, preservation, video data management, 3D objects, and peer to peer.