Inspired by the book Private Truths, Public Lies by Timur Kuran, the present thesis tries to examine the intricate relationship between public opinion and the media. In the first part of the thesis, the key theoretical concepts are exposed (public opinion, preference falsification, spiral of silence, social pressure, agenda setting, etc.). In addition, the theoretical landscape of the debate about the phenomenon of public opinion has been outlined and the most important factors determining the dynamics of public opinion singled out. In the second part of the thesis, the example of the Croatian referendum on the definition of marriage, carried out in 2013, is invoked to illustrate the media’s influence on ideological issues. Tackling one of the hottest of these issues – gay marriage, it hardly surprising that the referendum provoked intensive emotional reactions (on both sides) and deeply divided the Croatian society. The thesis attempts at identifying the most prominent reasons and motives influencing citizens’ siding with the YES and the NO party, respectively. It also attempts at identifying the most important institutional forces of social pressure (NGO’s, religious communities, political parties) and describing their public relations strategies during the media campaign. Lastly, it gives an overview of the most important aspects of the campaign, and – based on an analysis of selected media contents – tries to estimate the impartiality and professionalism of the media coverage of the campaign. Despite the fact that the Croatian government and the Croatian mass media did their best to sway the larger public in its attitude, they failed. The concluding part of the thesis speculates about the possible causes of this unexpected outcome.