The aims of the present study were to develop diagnostic criteria of Internet addiction for adolescents and to examine the discriminating potential and validity of diagnostic criteria by an empirical community study among adolescent populations. We developed 13 candidate diagnostic criteria for characteristic symptoms of Internet addiction in adolescents. A total of 468 adolescents completed the Chen Internet Addiction Scale (CIAS) and were systematically assessed for Internet-using behaviors by seven psychiatrists using the diagnostic interview schedule. The sensitivity, specificity, and diagnostic accuracy of the 13 candidate diagnostic criteria were analyzed with references to the interviewers' global clinical impressions and CIAS results. The cutoff point of the diagnostic criteria to differentiate the Internet-addicted subjects with nonaddicted ones was then determined by the best diagnostic accuracy and the receiver operating characteristic curve. This study selected nine of the 13 candidate diagnostic criteria to construct the diagnostic criteria of Internet addiction for adolescents, which were composed of three main criteria: characteristic symptoms of Internet addiction, functional impairment secondary to Internet use, and exclusive criteria. The diagnostic criteria had high diagnostic accuracy, specificity, negative predictive value, accepted sensitivity, and accepted positive predictive rate. The validity of the diagnostic criteria proposed in this study was further confirmed by comparing the demographic and Internet-using characteristics between those with and without Internet addiction. The diagnostic criteria for Internet addiction can provide health care professionals with a means to communicate and make comparisons of clinical cases.