Background and objective: Computers and the Internet have become an integral part of today's life. Problematic gaming is related to adolescent's health. The aim of our study was to evaluate the prevalence of Internet addiction among 13–18-year-old schoolchildren and its relation to sex, age, and time spent playing computer games, game type, and subjective health evaluation. Materials and methods: A total of 1806 schoolchildren aged 13–18 years were interviewed. The evaluation of Internet addiction was conducted by the Diagnostic Questionnaire according to Young's methodology. The relation between the choice of computer games type, time spent while playing computer games and respondents’ Internet addiction were assessed by using multivariate logistic regression analysis. Results: One-tenth (10.6%) of the boys and 7.7% of the girls aged 13–18 years were Internet addicted. Internet addiction was associated with the type of computer game (action or combat vs. logic) among boys (OR = 2.42; 95% CI, 1.03–5.67) and with the amount of time spent playing computer games per day during the last month (≥5 vs. <5 h) among girls (OR = 2.10; 95% CI, 1.19–3.70). The boys who were addicted to the Internet were more likely to rate their health poorer in comparison to their peers who were not addicted to the Internet (OR = 2.48; 95% CI, 1.33–4.62). Conclusions: Internet addiction was significantly associated with poorer self-rated health among boys.