Problematic internet use shows increasing growth among adolescents, also in Slovak context. It can be defined as symptom of addiction containing excessive and compulsive use of the internet, low social comfort, lack of social relations, loneliness, impulsivity, low self- esteem and anxiety. There are many factors which play role in problematic internet use, as lack of social and parents' emotional support, lack of communication with parents, low self-esteem of individuals. This study was conducted aimed to analyse family functioning (cohesion, adaptability, communication and satisfaction) as predictor of problematic internet use among Slovak adolescents.- The sample included 106 adolescents in the age from 15 - 19 (M = 17.8, SD = 1.2)vertical bar. The study tools included: Problematic internet use questionnaire PIUQ (Demetrovics, Z., Szeredi, B., & R6zsa, S. 2008) which distinguishes three factors of problematic Internet use-obsession, neglect and control disorder, Family Adaptability and Cohesion Evaluation Scale FACES IV, Family Communication Scale FCS and Family Satisfaction Scale FSS (Olson, 2010). The multiple regression analysis (method enter) was used. Findings showed that family variables (balanced, enmeshed and disengaged cohesion, balanced, chaotic and rigid flexibility, communication and satisfaction) explain 20% variance of obsession, 24 % variance of neglect and 15% variance of control disorder. The only significant and the strongest predictor of three dimensions of problematic internet use was enmeshed cohesion (beta =.31-.36, p < 0.01). Results indicated that excessive cohesion can lead to escape from family and family tasks toward friends and activities in internet. Findings supported the relevance of family relations, analysed by systemic perspective, in the problematic internet use among Slovak adolescents.