Adolescents perceive the Internet as a natural communication medium and a tool for processing information. They can access it from a mobile phone, personal computer and many other portable devices. The area of social networks, which is a common part of the adolescents’ life and style, has become the phenomenon of the young generation, but is also associated with a number of risks. The research analysed the impact of the use of modern information and communication technologies on the behaviour of six adolescent psychiatric patients. The specially designed qualitative research and analyses of technical documentation, interviews and observations have been used to compile case studies of people hospitalized due to the worsening of their mental condition. Informants showed symptoms of overuse of the Internet, or even addiction. In the online environment, they were looking for trust, friends, role models, advice, support and praise. The high number of their virtual contacts sharply contrasted with the low activity in their real life. Using the Internet intensively, they were compensating for the unfulfilled needs in their family and school life, ventilating their worries, fears and psychological pain. They got into a vicious circle, which, without expert help, steadily kept intensifying. A harmonious family background, good environment at school and classroom, actual good friends and adequate leisure time play an essential role in dealing with the overuse of or dependence on online activities. It is important that the adolescent experiences success, reward, and positive motivation. Appropriate psychotherapy and counselling services may help in cases of such problems.