The aim of this study was to search for correlates of cognitive impairment in patients with paranoid schizophrenia among clinical, demographic, anamnestic and biochemical markers (NSE, S100B protein, BDNF, hs-CRP). Patients with paranoid schizophrenia (n=125) were examined using the Brief Assessment of Cognitive Function in Schizophrenia, the Rey-Osterrieth Complex Figure task, and a number of clinical scales including the Positive and Negative Syndrome Scale. The majority of patients demonstrated cognitive impairment. The type of impairment was highly heterogeneous and individual. Relationships were found between the degree of executive functioning and family history of mental illness; working memory and age of onset of schizophrenia; and visual memory and psychopathological symptomatology. Negative and affective symptoms were not significantly associated with cognitive functioning. Treatment with first generation antipsychotics was associated with a more frequent impairment of motor skills, and concomitant anticholinergic drugs, with reduced accuracy. Use of second-generation antipsychotics only was associated with better accuracy, working memory and speech fluency. Among the patients, 21.4% had signs of a systemic inflammatory response, indicating a possible role of inflammatory response in the development of schizophrenia. CRP, S100B and NSE levels reflected features of the course of illness and therapeutic response. Patients with lower concentrations of BDNF were characterized by lower processing speeds.