Despite the significant contributions from previous studies about the prevalence of problematic Internet use (PIU) among adolescents in Europe, important questions remain regarding adverse consequences of PIU. This study aims to assess the relation between duration of Internet use and adverse psychosocial effects among adolescents from six European countries. The final sample included 7,351 adolescents (50.8% male and 49.2% female; mean age: 14.6±1.90) recruited from randomly selected schools within the six study sites. Results showed that 12.9% of adolescents used Internet more than 20 hours per week. There was a significant relationship between duration of Internet use and frequency of alcohol, tobacco, cannabis and other illegal drug use. Duration of Internet use is also significantly associated with school problems, with use of slot machines and with other psychosocial problems. These findings highlight the need to strengthen preventive efforts for reducing PIU and related consequences among adolescents.

Key Words: Internet, adolescents, psychosocial problems.