This study presents the profiles of heavy Internet users and provides empirical evidence that it is not how much time university students spend online but what they do online that is associated with academic grades and psychological adjustment. Using a nationally representative sample from Taiwan, we employed K-mean cluster analysis and identified profiles based on nine Internet practices in which users engaged. Female heavy users favoring information seeking and chatting had better academic performance but tended to feel more depressed than nonheavy users, while those favoring information seeking, chatting, and online games had lower academic grades and greater loneliness, physical illness, and depression scores than nonheavy users. In contrast, only male heavy users favoring online games had lower academic grades, whereas those who favored information seeking, chatting, and online games were more likely than nonheavy users to feel physically ill and depressed.