The study investigated Internet gambling involvement and pathological gambling among Hong Kong adolescents aged 12–19 years. The diagnostic and statistical manual (4th edition) multiple response format for juveniles (DSM-IV-MR-J) (Fisher in J Gambl Stud 16:253–273, 2000) was filled by 1,004 students (597 boys, 407 girls) recruited by random selection of classes. The response rate was 86.6 %. Results indicate that more respondents participated in land-based gambling than Internet gambling (63.5 vs. 3.5 %) but online gamblers are 1.5 and 3.2 times more likely to develop pathological and at-risk gambling than non-Internet gamblers. Using the DSM-IV-MR-J criteria, 5.7 and 22.9 % of the Internet gamblers could be classified as at-risk gamblers and pathological gamblers, respectively. Majority (94.3 %) wagered online at home, and 91.4 % made their first bet before 18 years. Many perceived Internet gambling as a trendy (71.4 %) and safe entertainment (54.3 %). Problematic Internet gambling was significantly associated with the male gender, school grades, online gambling frequency, amount wagered and a gambling family environment. Survey results have implications for gambling research and preventive programs.