Background and aims: The aims of this study were to examine the association between social skills deficits and Internet addictio n and activities in adolescents with attention-deficit/hyperactivity disorder (ADHD) as well as the moderators for this association. Methods: A total of 300 adolescents, aged between 11 and 18 years, who had been diagnosed with ADHD participated in this study. Their Internet addiction levels, social skills deficits, ADHD, parental characteristics, and comorbidities were assessed. The various Internet activities that the participants engaged in were also examined. Results: The associations between social skills deficits and Internet addiction and activities and the moderators of these associations were examined using logistic regression analyses. Social skills deficits were significantly associated with an increased risk of Internet addiction after adjustment for the effects of other factors [odds ratio (OR) = 1.049, 95% confidence interval (CI) = 1.030-1.070]. Social skills deficits were also significantly associated with Internet gaming and watching movies. The maternal occupational socioeconomic levels of the participants moderated the association between social skills deficits and Internet addiction. Conclusions: Social skills deficits should be considered targets in prevention and intervention programs for treating Internet addiction among adolescents with ADHD.