Purpose: Increasing research on Internet addiction makes it necessary to distinguish between the medium of Internet and its specific applications. This study explores the relationship between time spent on various Internet applications (including online gaming) and Compulsive Internet Use in a large sample of adolescents. Methods: The 2007 (N = 4,920) and 2008 (N = 4,753) samples of a longitudinal survey study among adolescents were used, as well as the 2007-2008 cohort subsample (N = 1421). Compulsive Internet Use was predicted from the time spent on the various Internet applications in two cross-sectional multiple linear regression models and one longitudinal regression model in which changes in behavior were related to changes in Compulsive Internet Use. Results: In both samples, downloading, social networking, MSN use, Habbo Hotel, chatting, blogging, online games, and casual games were shown to be associated with Compulsive Internet Use. Off these, online gaming was shown to have the strongest association with Compulsive Internet Use. Moreover, changes in online gaming were most strongly associated with changes in Compulsive Internet Use over time for the longitudinal cohort. Conclusions: A clear relationship was shown between online gaming and Compulsive Internet Use. It is further argued that a subgroup of compulsive Internet users should be classified as compulsive online gamers. (C) 2010 Society for Adolescent Health and Medicine. All rights reserved.