According to some data, about 50% of the student population experiences some symptoms of depression, which is becoming an increasingly common problem among young people. The aim of this study was to examine the role of dysfunctional attitudes and intrusive negative thoughts in the development of depressive symptoms, as well as the mediating effect of positive rumination and suppression of positive emotions on these relationships. Four hundred twenty six students participated in the research, 46 males and 380 females. The age of the respondents ranged from 18 to 26 years, with the average of 22 years. Most of the respondents attend the University of Zagreb and the University of Rijeka, although students from other Croatian universities also took part in the survey. The instruments used were: General Data Questionnaire, Dysfunctional Attitudes Scale (DAS-17), Responses to Positive Affect Questionnaire (RPA), Persistent and Intrusive Negative Thoughts Scale (PINTS), and Depression, Anxiety and Stress Scale (DASS-21). Research was conducted via online Lime Survey tool. A moderate positive correlation was observed between dysfunctional attitudes and depression, as well as between intrusive negative thoughts and depression. Hierarchical regression analysis found that the regulation of positive emotions explains 10% of the variance of depression, in addition to dysfunctional attitudes and intrusive negative thoughts. Partial mediation effects of positive rumination and suppression of positive emotions on the relationship between dysfunctional attitudes/intrusive negative thoughts and depression were determined. The research points to various factors that can contribute to the development of depressive symptoms in students, with an emphasis on the regulation of positive emotions, which has been researched to a much lesser extent. The obtained results and validated questionnaires can be used in future research and counseling.