This article demonstrates how self-diagnostic information (presence of symptoms on an inventory) influences the risk perception of Internet addiction disorder (IAD). The authors also highlight 2 tendencies—self-positivity bias and online social support—that are characteristics of risk perception of IAD. In 3 studies, it was found that if no contextual information was provided, respondents estimated their risk of IAD as higher than when contextual information (symptoms) was provided. They were also less prone to self-positivity (i.e., the disposition for people to estimate their risk as lower than others). Finally, our research provides evidence that online social support moderates these effects.