102 patients after mitral valve replacement and 120 patients after aortic valve replacement were included in the observation retrospective study. By the moment of mitral valve replacement age amounted 3 months - 18 years (7,7±5,1 years in average), terms after the operation - 1-13 years (5,3±2,9 years in average). By the moment of aortic valve replacement age amounted 3 months - 18 years (12,7±3,3 years in average), terms after the operation - 1-23 years (4,6±3,2 years in average). All patients underwent complex investigation, veloergometry was carried out in the absence of contraindications. Quality of life was studied using the scale for patients with cardiovascular diseases. Statistically significant improvement of functional status was observed after the operation: 93% of all patients were related to I-II functional classes (p<0.001). Unsatisfactory indices of coagulogram were observed in 54% of patients after mitral valve replacement and in 25% of patients after aortic valve replacement. Among patients with artificial mitral valve thromboembolic complications were observed in 8 (7.8%) cases, hemorrhages - in 5 (4.9%) cases. Among patients with replaced aortic valves acute stroke was observed in 9 (8.8%) patients, hemorrhages - in 11 (10.7%) of patients. Decreased physical capacity was observed in patients with lesser indexed prosthetic orifice area. It is drawn a conclusion that in long terms after mitral and aortic valve replacement children and adolescents present with marked physical improvement. Physical capacity depends on indexed prosthetic orifice area. Embolism, hemorrhage and prosthetic dysfunction are the most frequent complications.