The aim of present study was to investigate relationships between problematic internet use and depression, anxiety and stress, and to determine the predictive strength of problematic internet use on depression, anxiety and stress. Research group of the study was composed of 543 university students (154 male and 378 female). The age of university students including research group differed between 17 and 28, the mean age was 18.49 (SD = 1.06). In current study, Problematic Internet Use Scale, Depression, Anxiety and Stress Scale and personal data form developed by researchers were used as measures. Research results indicated that there were significant associations between problematic internet use and depression, anxiety and stress. As a consequence of regression results, problematic internet use was a significant predictor of depression, anxiety and stress. The results were discussed in the light of the relevant literature.