Wilson disease (WD) is a rare hereditary disorder of copper metabolism, based on of the ATP7B gene mutation, resulting in defect of cooper excretion, which leads to accumulation of cooper in tissues and internal organs (especially in the liver and brain). The basic principle of diet therapy for patients with WD is a diet with reduced copper content, adherence to which is accompanied by significant dietary restrictions, so patients with WD, compared to other liver diseases, represent the most difficult contingent for adjustment of diet. The aim: to assess of the effect of diet therapy with modification of the protein component on nutritional status of patients with WD. Material and methods. The study included 33 patients (15 men and 18 women, 31.4±10.2 years old) with WD. All patients had liver damage: non-cirrhotic stages (NCC) - in 12 (36.3%) patients, liver cirrhosis (LC) - in 21 (63.7%) patients. Out of the last, 14 (66.7%) patients had compensated LC, 7 (33.3%) patients had decompensated LC. The average age of the patients. All patients were divided into two groups, comparable by body mass index. For 2 months outpatients of the 1st group (n=17) received a specialized diet with a modification of the protein component, made by incorporating 20 g of dry composite protein mix (containing 50% protein in the form of milk protein concentrate, 4% dietary fiber) into the daily diet. Outpatients of the 2nd group (n=16) received the same diet without modification. All patients were provided anthropometry, including shoulder circumference and triceps skin-fold measurement, and analysis of the body mass composition with bioimpedance analyzer, the index of lean mass was additionally calculated. Clinical and biochemical blood tests were also conducted for all patients. Results and discussion. As a result of the diet therapy, statistically significant (p<0.05) changes were observed in patients of the 1st group who received a diet with a modification of the protein component: an increase in the index of lean mass (by 3.0%) and circumference of the shoulder muscles (by 2.3%), serum total protein and albumin (by 7.9 and 6.1%), an increase in the absolute number of lymphocytes (by 18.8%) and decrease in serum total bilirubin (by 20.2%). A statistically significant decrease in the level of free copper was observed in both groups (by 2.1 and 1.8 fold). Conclusion. The use of a specialized diet with a modification of the protein component, based on the inclusion of a protein composite dry mix in the diet, improves the nutritional status indicators in patients with Wilson disease.