The article presents data on the state of the paravertebral muscles studied by magnetic resonance imaging (MRI) in 26 patients with idiopathic scoliosis with various degrees of spinal deformity. A decrease in muscle area and fatty degeneration, expressed from the concave side, were noted. The area of the paravertebral muscles on the concave side in deformity of 70–90 ° significantly differed from the area of the muscles on the convex side. The average degree of fat infiltration of various muscles along the concave side ranged from 14 to 28 %. The degree of fatty degeneration and hypotrophy of the paravertebral muscles should be taken into account when preparing for surgery, during its performance and when developing a rehabilitation program in the postoperative period.