The purpose of this study was to determine whether using the Internet for different activities affects the quality of close adolescent relationships (i.e., best friendships and romantic relationships). In a one-year longitudinal study of 884 adolescents (Mean age = 15, 46% male), we examined whether visiting chat rooms, using ICQ, using the Internet for general entertainment, or participating in online gaming predicted changes in the quality of best friendships and romantic relationships. Multiple regression analyses indicated that Internet activity choice influenced later relationship quality in both best friendships and romantic relationships. Using instant messaging (ICQ) was positively associated with most aspects of romantic relationship and best friendship quality. In contrast, visiting chat rooms was negatively related to best friendship quality. Using the Internet to play games and for general entertainment predicted decreases in relationship quality with best friends and with romantic partners. These findings reflect the important and complex functions of online socialization for the development and maintenance of relationships in adolescence.