Thesis about situation of the digital preservation and analysis of the present tools available to confront the responsibility of the preservation of this property and to guarantee their public access in the time. The search, beginning from a reflection of base on the concepts of preservation/conservation of the digital resources, with the different approaches of Librarians and Archivists and the interest interdisciplinary, introduces criteria and strategies of collection, some projects, studies and international initiatives, some examples of systems for the long term preservation of the digital resources from 1996 at today, internationals and in Europe. About the legal matters they confront themselves the author's rights, the legal deposit ...