The internet is an integral tool for information, communication, and entertainment among adolescents. As adolescents devote increasing amounts of time to utilizing the internet, the risk for adopting excessive and pathological internet use is inherent. The study objectives include assessing the characteristics and predictors of excessive internet use and evaluating the prevalence of pathological internet use among Greek adolescents. A cross-sectional study design was applied to this effect. The study population (n = 897) consisted of a random sample of adolescents residing in Athens, Greece. Self-completed questionnaires, pertaining to internet access characteristics and Young's Internet Addiction Scale (YIAS) score, were applied in order to investigate the study objectives. The multivariate regression analysis indicated that the most significant predictors of overall internet use included accessing the internet via one's own home portal and for the purpose of social interaction. Internet access via the school environment was a significant deterrent among low (1-3 h/week) internet users, while access via internet cafés was a significant predictor for high (11-20 h/week) internet users. Moreover, accessing the internet for the purposes of game playing was the most significant predictor for excessive (>20 h/week) internet use. The prevalence of borderline internet use among the study population was 12.8%, while 1.00% reported addictive internet use. Also, 10.4% of male excessive internet users reported addictive internet use (p < 0.0001). In conclusion, excessive internet use is predicted solely by the location of internet access (own home portal) and the scope of internet use (i.e., sites relating to socialization and game playing) and may lead to internet addiction, particularly among male adolescents.