Objective. A comparative analysis of the immediate results, the course of the hospital period of operations “Maze IIIB” in the treatment of atrial fibrillation, complicated by arrhythmogenic mitral regurgitation. Material and methods. Retrospectively, case histories of 310 patients who were operated on from one department to another between 2010 and 2017 were analyzed. These patients underwent surgical treatment atrial fibrillation of open heart in the modification of Maze III, using cryo-ablation and radiofrequency ablation with or without mitral valve annuloplasty. An original technique was used, which included a combination of incision and suture and ablation in the left and right atria, in combination with annuloplasty atrioventricular valves. Patent No. 2017 120 391 dated 06/03/17. For the purity of the study, patients with congenital pathology and coronary heart disease, patients with myxomatous mitral valve degeneration who underwent multicomponent reconstruction were excluded from the analysis. Patient groups were identified as follows: patients who underwent surgical treatment of atrial fibrillation with or without tricuspid valve annuloplasty (group 1 – n=67, group 2 – n=243), where surgical treatment was performed for atrial fibrillation and annuloplasty of mitral and tricuspid valve. Patients of group 1 were slightly younger than patients of group 2, however, the remaining gender, anthropometric, anamnestic data, as well as the presence of concomitant pathology were significantly comparable, allowing us to compare the course of the surgical, early postoperative stage, the presence of complications and treatment results. Results. Hospital mortality in group 1 was 1.5% (n=1) and 1.6% (n=4) in group 2, did not significantly differ. Implantations of pacemaker was 10.4% (n=7) in the first group and 12% (n=29), taking into account the sick sinus syndrome, there were no significant differences in comparing the two groups. Sinus rhythm retention in group 2 was significantly different from group 1 (93% versus 84%; p<0.001). The area under the ROC curve is 0.7 (for the model of left atrial enlargement), which indicates the likelihood of arrhythmia after surgery when the size of the drug is equal to or more than 189 ml initially. Conclusion. The Maze IIIB, which is used in surgery for atrial fibrillation complicated by arrhythmogenic mitral and tricuspid insufficiency, is highly effective in restoring sinus rhythm according to the results of the early postoperative period. Correction of moderate arrhythmogenic mitral valve insufficiency affects the immediate results of the operation, which is the determining prospect of using a simple technique in combination with surgical treatment of atrial fibrillation. The diameter of the mitral valve of more than 35 mm without correction, as well as the volume of the left atrium of more than 189 ml, are associated with a risk of arrhythmia return after surgery.