Mental health is an important aspect of health and it is a prerequisite and fundamental feature of the quality of life itself. Just as a person preserves and nurtures his physical health, the need to preserve and promote mental health is the same, if not greater. Sometimes mental disorders appear in people either because of a positive family history, surviving a certain trauma, inability to cope with the stress of everyday life, inability to contribute to the community to the extent that the individual wants to, etc. Schizophrenia and bipolar affective disorder are just some of the mental disorders from which a person can suffer from. The aim of this research is to see the level of theoretical knowledge of nursing students about bipolar affective disorder and schizophrenia for the purpose of quality health care. Subjects and methods: The research is conducted on full-time and part-time students of the 3rd year of undergraduate nursing studies in Rijeka and Varaždin. A total of 80 respondents, chosen by a non-probabilistic method, a convenient sample, participate, and their level of knowledge is tested through online questionnaires about these disorders. Results: The conducted research confirmed hypothesis 4, which states that students of both studies in Rijeka and Varaždin have more knowledge about schizophrenia than about bipolar affective disorder. The research did not confirm hypothesis 1, which stated that the level of knowledge is lower among full-time students in the 3rd year of undergraduate professional nursing studies in Rijeka and Varaždin compared to part-time students in the 3rd year of the same universities. Hypothesis 2: the level of knowledge is higher among full-time students of the 3rd year of undergraduate professional studies in Rijeka compared to full-time students of the 3rd year of undergraduate professional studies in Varaždin was also not accepted, as was hypothesis 3 that the level of knowledge is higher among part-time students of the 3rd year of undergraduate professional studies of professional studies in Rijeka in relation to part-time students of the 3rd year of undergraduate professional studies in Varaždin. Conclusion: The analysis of the data proved a statistically significant difference, and it was confirmed that the students of the undergraduate study of nursing in Rijeka and Varaždin have more acquired knowledge about schizophrenia than about bipolar affective disorder.