French architectural office Lacaton and Vassal owns a work in which the appropriation of preexistences is recurrent: through the use of commercial prefabricated structural systems, by incorporating the preexistent building to new projects, and through the permanence and maintenance of the existent building. This research is aimed to analyze such different appropriation methods and to recognize new critical motivations, within a contemporary context, for using this strategy in the conception of architectural projects. To this end, the objective pursued was (1) to describe, analyze, and historically contextualize this concept; (2) to recognize the different appropriation methods used by Lacaton and Vassal; (3) to compare this approach to appropriation with the approach of other contemporary architects - Smiljan Radic and Santiago Cirugeda, and (4) finally, to provide a deeper analysis of Lacaton and Vassal s intervention at the Palais de Tokyo (Paris), because it enlightens several concepts that are critical of the discipline of architecture and are also, somehow, a consequence of the core idea of appropriation, as well as they show some contradictions within these architects discourse.