Illegal political activity has always been part of a democratic society. Despite this, not much is known about young people’s involvement in these political activities. Research portrays political influence attempts of this kind in different terms; as troublesome for the democratic political system, as expressions of conscious decisions vital for humanity’s future, and yet other times as illustrations of a coming-of-age rebellion. Overall there is a lack of collective knowledge on illegal political activity, and especially in adolescence – the age period when these political activities seem to peak. The aim of this dissertation is therefore to enhance knowledge of involvement in illegal political activity in adolescence. This dissertation addresses this task in four empirical studies. Results show that mostly boys engage politically with illegal political means. Adolescents involved are also interested in politics, believe in their own abilities to take part in political activities, have long-term political goals, and approve of violent political tactics. In addition, these activities also seem to associate with a challenge of authority. This could be seen in how political dissatisfaction was translated into illegal political activity, and in the way these activities seemed to be reactions to a non legitimized parental authority. Besides authority challenges, these activities are likely the result of important peer relations; influences from peers with experiences of illegal political activity seem to be a most probable answer to why adolescents adopt these political means. Taken together, the results of this dissertation show that adolescents involved in illegal political activity are well-equipped for political involvement, challenge authorities in most contexts of their lives, and are likely to adopt these political means from already involved peers.