Cognitive disorders after stroke are one of the main causes of disability in daily activities. The main aim of this study was to investigate the frequency of post-stroke dementia, post-stroke mild cognitive impairment (MCI) and post-stroke amnestic MCI at different times after first-ever stroke; 196 patients were included in the study. In addition, cognitive disorders and their clinical course were studied. Frequency of post-stroke dementia was about 10% at all evaluation times; most patients had post-stroke MCI. Of the cognitive functions investigated, mental speed and calculation were most frequently affected. Performance on almost all cognitive tests was improved 6 and 12 months after stroke. Thus, while the frequency of post-stroke dementia is low, the frequency of post-stroke MCI is high, but improvement of cognitive function is possible.