The starting point of this speech is a theoretical overview of the concept of participation and of the new role of users in web 2.0 2 platforms which allow them to create, select and re-elaborate audiovisual contents. The final purpose is to analyze the changing role of active audiences in a so-called “user generated tv”, 3 together with users’ possibilities to redefine the public sphere by modifying the agenda setting, newsmaking rules and the imaginary of mainstream media and to create, in this manner, a cultural common value of TV through its social and participated use.