The aim of this project was to translate, culturally adapt and validate the Internet Addiction Test (IAT) in Greek adults. Twenty-one post-graduate medical students participated in the cultural adaptation procedure and 151 both post- and under-graduate medical students in the validation process. The internal consistency shown by a Cronbach's alpha was 0.91. Two-week test-retest reliability was rtt = 0.84, p < 0.001. Face validity was affirmed by 83.6 % of the students. In terms of convergent validity, the hours of daily internet use were positively correlated with IAT score (rho = 0.48, p < 0.001). Moreover, IAT scores were higher in students that reported use of online gambling (40.5 vs 29.2, p = 0.004), pornographic sites (36.5 vs 28.0, p = 0.003) and online games (35.6 vs 28.2, p = 0.009). Exploratory factor analysis revealed three interpretable factors for the IAT, "Psychological/Emotional Conflict", "Time Management" and "Neglect Work", that showed good internal consistency and concurrent validity, explaining 55.3 % of the variance. The Greek version of IAT has shown good psychometric properties, comparable with the original IAT and the previously published translated versions, and can be a useful tool in future studies on internet addiction.