Because of the necessity of objective instrumental methods for assessing the state of skeletal musculature in patients with Duchenne muscular dystrophy, the aim of our work was to evaluate the correlation between manual methods of assessment of the muscle strength and the results of magnetic resonance imaging (MRI) of the skeletal muscles of lower limbs. We have examined 15 corticosteroid-naive patients with Duchenne muscular dystrophy. Patients were divided into 2 groups: ambulant patients (average age 8.1 years) and non-ambulant patients (mean age 12.7 years). Muscle strength of lower extremities of all patients has been evaluated by Medical Research Council scale and MRI of skeletal muscles of the pelvic girdle, thighs and lower legs has been performed. The following results have been obtained: ambulant patients have been characterized by a high correlation of MRC scale and MRI of the lower extremities in the evaluation of the pelvic girdle and thighs muscles and the total score (pelvic girdle, thighs and lower legs) and salient correlation in the evaluation of the lower legs muscles. Non-ambulant patients have been characterized by moderate correlation in the evaluation of pelvic girdle and thighs muscles, as well as the total score of lower limbs. There was no correlation between MRC and MRI results in the muscles of the lower legs. Magnetic resonance tomography is able to reliably estimate the degree of fatty infiltration in Duchenne muscular dystrophy and is the method of choice in the diagnosis and evaluation of the severity of this disease.