Internet gambling participation is rapidly increasing, however little is known about potential links between internet gambling and problem gambling. This study examined the predictors of online problem gambling and whether these differed from established predictors of offline problem gambling. Data were obtained online in response to posts on 32 international gambling websites (n = 1,119). Potential correlates included demographic questions, gambling activities, frequency of gambling, and reasons for gambling online. Multinomial logistic regression revealed that compared to non-problem gamblers, online problem gamblers were more likely to be male, smoke cigarettes, gamble alone, have a disability, lie about their age online, gamble online for more than 4 h at a time, engage in two or more online gambling activities regularly, gamble after a near miss, and drink alcohol while gambling online. Therefore, characteristics predictive of offline problem gambling are similar to those predicting online problem gambling. As a result online gambling could potentially be problematic for those individuals who have problems with gambling more generally.