Sažetak The aim of the paper is to explore adolescents' manifestations of the Facebook social network usage and to determine dimensions of adolescent behaviour on the social network. A sample of respondents (N = 134) is made up of second grade high school students. The research results show that there are three dimensions of the virtual activity of adolescents: intrinsic, extrinsic and risk dimension. Each dimension includes different domains of activities that potentially point to the educational implications of virtual activity (information and communication, socialization, addiction and violence). The results of the t-test show that there is no difference in intrinsic and extrinsic behaviour with respect to gender, but there is a difference in the implications for risk behaviour - female adolescents are more prone to identifying the virtual world with actual social networks and are more exposed to virtual violence, while male adolescents are more inclined to participate in virtual violence, and their virtual activity favours the creation of virtual addiction.