Aim. The purpose of the study was an assessment of the prevalence of depressive symptoms and characteristic of cognitive functions in patients with hepatitis C before and after three month treatment with interferon-alpha plus ribavirine. Subject and methods. One hundred hepatitis C patients without decompensated liver function and without organic or psychotic disorder were assessed using the Hamilton Depression Rating Scale, the Stroop Test and the Trail Making Test. Results. Significant depressive symptoms were present in 18% patients at enrolment. Three-month therapy with IFN+RBV brought about depressive symptoms in additional 25% patients and did not influence their cognitive functions. Patients who had depression at enrolment exhibited significant worse verbal working memory than patients with interferon-alpha induced depression at the second assessment. Patients without depressive symptomatology both before and after IFN+RBV therapy significantly improved on tests of psychomotor speed and verbal working memory after three-month IFN+RBV therapy. Conclusion. Clinical and neuropsychological differences may suggest distinct pathogenesis of spontaneous and interferon- induced depression.