Internet gambling among adolescents is a growing phenomenon that has received little attention to date. This study examines associations between Internet gambling and the severity of gambling, substance use (SU), and delinquent behavior among 1,870 Quebec students aged 14 to 18. The results show a higher proportion of Internet-gambling (IG) students reporting problematic substance use and delinquency, compared with nongamblers (NG) and non-Internet gamblers (NIG). Furthermore, a higher proportion of at-risk and probable pathological gamblers are found among IG compared with NIG. A moderating effect (Baron & Kenny, 1986) of the gambler categories (NIG, IG) was found in the relationship between the associated problems and the severity of gambling. Among IG, the severity of delinquency and of substance use contributes to explaining gambling severity whereas, among NIG, the severity of delinquency is the only factor that significantly contributes to such an explanation. Discussion of the results is based on Jessor, Donovan, and Costa's (1991) general deviance syndrome theory.