University students are one of the most Internet-related groups in society. They are more likely to use the Internet for socialization and academic-development purposes. These needs lead some students to excessive Internet use, the most decisive marker of problematic Internet use. The aim of this study is to examine problematic Internet use with respect to the purpose of Internet use, irrational beliefs, feelings of inferiority, and gender. Data have been collected using a demographic information form and the Problematic Internet Use Scale, Feelings of Inferiority Scale, and Irrational Beliefs Test. Statistical Package for Windows is used for data analysis. Descriptive statistics, correlation analyses, ANOVA, and regression analyses have been conducted to examine the data. The results show that students who use the Internet for social media and playing games have a significantly higher level of problematic Internet use than those who use the Internet for academic purposes. According to the regression analysis results. discouragement and the negation of self-worth (the two sub-dimension of inferiority feelings) explain 25% of the total variance in problematic internet usage. They are followed by the three subdimensions of irrational beliefs, namely desire for approval, blaming tendencies, and perfectionism. These variables explain 2% of the total variance in problematic internet usage. Lasltly, gender (being male) explain 1% of the total variance in problematic internet usage. At the end of this study,predictors are examined according to gender seperately and results indicate that discouragement and the negation of self-value explain 25% of the total variance in problematic internet use among female and male students whereas, irrational beliefs predict only female students' problematic internet use with its 4% explanatory power. Based on these results, having discouragement and the negation of self-worth be considered as highly important variables in the problematic Internet use of university students is strongly recommended. However, despite the background in the literature on cognitive factors in problematic Internet use, their small effect in this study shows the relationship of irrational beliefs with problematic Internet use to require more research.