Objective. To study a role of parenchymal white matter lesions and lesions of the white matter underlying the cortical grey matter in cognitive impairment in patients with multiple sclerosis (MS). Material and methods. We examined 33 patients with clinically definite RRMS in clinical remission. Cognitive performance was assessed with neuropsychological and psychometric tests. MRI (1.5 tesla) was used to assess volume and localization of focal demyelination in the cerebral cortex. Results. The volume of juxtacortical brain lesions in the white matter had a negative effect on the correct performance on neuropsychological tests. The volume of parenchymal white matter lesions had a negative effect on the speed of task performance. Conclusion. The results suggest that MS patients had multiple cognitive impairments.