This review paper provides analyses confirming correlation between various brain regions activity, particularly its prefrontal portions, and schizophrenia patients' performance in verbal fluency tests. Various factors modifying patients' performance in the aforementioned tasks were singled out and discussed. Systematically we have reviewed the results of non-verbal fluency tests conducted in the schizophrenic patients. The authors also summarizes findings of earlier studies stressing the role of semantic fluency as a predictor of first-episode psychosis. Verbal and non-verbal fluency tests engage complex cognitive processes and executive functions in patients. As a result, the interpretation of their results is often complicated and requires special competences. The tests are popular neuropsychological tools used for assessment of verbal memory, executive functions, visual-spatial abilities and psychomotor speed in patients with mental and neurological disorders. The aim of this paper is to discuss diagnostic tools used for measuring both types of fluency (verbal and non-verbal), test interpretation methods, as well as their usefulness in clinical diagnostics and scientific research.