Addictive disorders are being increasingly influenced by technology and one of the most recent developments is for gamblers to access games via the Internet. Prevalence data show that up to 10% of the population gamble online and studies have consistently indicated that Internet gamblers are particularly susceptible to developing gambling problems. Therefore, the purpose of this study was to explore differences between Internet and non-Internet gamblers to help determine why online gamblers are more likely to have gambling problems. Three hundred and seventy four participants (143 online gamblers, 172 males) from a large Canadian university completed an online questionnaire to investigate demographic, medium-related, comorbid psychological and cognitive factors with strong empirical support for contributing to problem gambling severity. Variables that significantly differentiated Internet and non-Internet gamblers in a univariate analyses were entered into a logistic regression to predict online gambling. A test of the full model was statistically significant, correctly classifying 77% of gamblers (64% of Internet gamblers and 85% of non-Internet gamblers). Cognitive distortions made an independent contribution to predicting Internet gamblers from those that had never wagered online. A hierarchical linear regression analysis revealed that cognitive distortions added significantly to problem gambling severity among online gamblers after controlling for other contributing variables. The findings have implications for clinicians working with Internet gamblers to specifically address thoughts related to luck, perseverance and illusion of control. As gambling technologies change and evolve, research needs to inform practice by identifying possible causal factors contributing to problem severity.