This study examined Internet and cybersex addiction in adolescents and how such behavior was associated with substance use (in particular, cigarettes, alcohol, and drug use).Participants were 312 adolescents, aged 14-16, who completed survey instruments. Study measures included demographic, toxic substance use, expectancies toward substances consumption, antisocial deviance proneness, Internet, and cybersex addiction variables.Descriptive, bivariate analyses, exploratory/confirmatory factor analyses, and structural Equation Modeling were performed. Nearly 60%, 26%, and 25% of adolescents reported having drunk alcohol, used drugs and smoked cigarettes respectively. Prevalence of Internet and cybersex risk scores was 23.3% and 6.8% respectively. Adolescents who reported having drunk alcohol, smoked cigarettes, or used drugs were more likely to report higher scores on both the Internet and the cybersex addiction scales. Proposed structural equation model explained between 25% and 42% of the variance of toxic substance use, 22% of the Internet addiction score, and 17% of cybersex addiction score. Expectancies toward substances consumption and antisocial deviance had a direct and significant influence on the study variables. Therefore, the overlap between substance use and Internet and cybersex addiction is the result of two common etiological pathways: positives expectancies toward substances consumption and a general tendency to antisocial behavior.