Multiple sclerosis is the most common chronic progressive inflammatory demyelinating disease of the central nervous system characterized by different clinical phenotypes, degrees of central nervous system damage and disease progression. Conventional magnetic resonance imaging has become a useful tool for diagnosis, differential diagnosis and monitoring disease progression. Recent innovations in magnetic resonance imaging give an opportunity to specify certain aspects of multiple sclerosis pathogenesis. This article is a review of diffusion-tensor magnetic resonance tomography and tractography usage in the brain and spinal cord of patients with different clinical phenotypes of multiple sclerosis. Main features of pathologically damaged white and grey matter observed using diffusion-tensor magnetic resonance tomography and tractography, correlations between different diffusion indices and disability are described. The problems of pathogenesis are discussed.