Using mediatization as the key concept, this article presents a theory of the influence media exert on society and culture. After reviewing existing discussions of mediatization by Krotz (2007), Schulz (2004), Thompson (1995), and others, an institutional approach to the mediatization process is suggested. Mediatization is to be considered a double-sided process of high modernity in which the media on the one hand emerge as an independent institution with a logic of its own that other social institutions have to accommodate to. On the other hand, media simultaneously become an integrated part of other institutions like politics, work, family, and religion as more and more of these institutional activities are performed through both interactive and mass media. The logic of the media refers to the institutional and technological modus operandi of the media, including the ways in which media distribute material and symbolic resources and make use of formal and informal rules.