The pictures in people's minds about the outside world are significantly influenced by the mass media, both what those pictures are about and what those pictures are. The agenda-setting effects of the mass media also have significant implications beyond the pictures created in people's heads. The media are the principal means by which a majority of people receive information about policy issues in general, and the EU in particular. The role of information provided by the mass media is substantially important to public opinion formation and change, especially on critical issues such as European Union enlargement. This chapter investigates why and how mass media affects the public opinion about the enlargement of the European Union.