The widespread use of internet has caused new psychological, social, and educational problems for the students. The aim of this study was to examine the quality of life in medical students who suffer from internet addiction. This cross-sectional survey was carried out in Tehran University of Medical Sciences, and a total of 174 fourth-to seventh-year undergraduate medical students were enrolled. The quality of life was assessed by WHOQOL-BREF questionnaire which covers four domains of physical health, psychological, social relationships, and the environment. For assessing internet addiction, we used Internet Addiction Test (IAT) of Young. The students with IAT score higher than 50 were considered as addicted. For evaluating academic performance, the students were requested to report their grade point average (GPA). The mean IA score (±SD) was 34.13±12.76. Twenty-eight students (16.90%) had IAT score above 50. The mean quality of life score in internet addicted group was 54.97±11.38 versus 61.65±11.21 in normal group ( P =0.005). Furthermore, there was a negative correlation between IA score and physical domain (r=-0.18, P =0.02); psychological domain (r=-0.35, P =0.000); and social relation domain (r=-0.26, P =0.001). Mean GPA was significantly lower in the addicted group. It seems that quality of life is lower in the internet addicted medical students; moreover, such students academically perform poorer in comparison with non-addicts. Since internet addiction is increasing at a rapid pace which may provoke considerable academic, psychological and social implications; as a result, it may require screening programs to the immediate finding of such problem to give consultations to prevent unwanted complications.