Citizens who take on a positive attitude toward the police are more inclined to obey the law, report crimes and cooperate with police activities. Previous research on the factors that influence the publics opinion about the police mostly focused on the influence of direct encounters with the police. Most people, however, only occasionally come into direct contact with the police. Their chances of coming into contact with the police through the media, on the other hand, are very high. Messages about the police are constantly spread in the news, in fictional shows, in movies and in social media. Therefore, the main goal of the dissertation is to examine the relationship between media use and peoples conceptions of the police. Since research shows that attitudes toward the police are most strongly developed during adolescence, the focus lies on adolescents beliefs about the police. Based on results from previous studies adolescents beliefs about the performance of the police (how effective are the police in crime control?), about the procedural fairness of the police (how fair are the decision-making processes and how respectfully do police officers treat citizens?) and about the distributive fairness of the police (do the police provide a similar service to different groups in society?) are examined, as well as the relationship with their global attitude toward the police. The first part of the dissertation studies the relationship between television use and adolescents attitude toward the police. More specifically it is analyzed to what extent the viewing of two types of programs, namely television news and fictional police shows, is related to certain beliefs about the police. This study is conducted within the framework of cultivation theory. Cultivation theory generally assumes that people who spend more time watching televisionare more likely to develop a world view that resembles how that world is depicted on television. To test this hypothesis a two-step research approach is used. Content analyses of television content (news and police shows) are combined with a survey among 1968 Flemish adolescents. The results show that adolescents exposure to news and Flemish and US-based police shows cultivates beliefs about the police that are in line with how the police are depicted in the respective genres. The strongest directrelationships are found between watching Flemish police shows and perceptions of the procedural fairness of the police. In addition, proceduralfairness beliefs mediate the relationships between fiction exposure andbeliefs about the performance and distributive fairness of the police. The doctoral research suggests that televisions depiction of the trustworthiness and respectfulness of police officers is a crucial factor in the cultivation of beliefs about several aspects of policing and in the development of a global attitude toward the police. The second part of the thesis explores the relationship between adolescents social mediause and their perceptions of the police. More specifically, it is studied how exposure to negative messages about the police on social media channels relates to adolescents beliefs about the police and to their general attitude toward the police. The study starts with the search for a theoretical framework for this largely unexplored research domain. Basedon an extensive literature review two hypothetical models are formulated. The first model builds on the uses and gratifications perspective andargues that adolescents can use social media to meet the information needs and social interaction needs they might experience concerning their beliefs about the police. The second model argues that exposure to social media messages about the police can also occur unintentionally and that exposure can consequently also predict beliefs about the police. Both models are confronted with the empirical data gathered among Flemish adolescents. Statistically the results show slightly more support for the uses and gratifications-model than for the effects-model. Theoretically, however, it is argued that the relationship between exposure to negativesocial media messages on the police and adolescents attitude toward the police is best understood from a combination of both models, in which each separate model has explanatory value but can only explain part of the process. The doctoral study shows that news viewing, police show viewing and social media use are all related to adolescents attitudes toward the police. Those relationships are found even after controlling for direct experience with the police, perceived neighborhood crime, gender, age, educational level and ethno-cultural position of the respondents.