Objective. Arrhythmias in adult patients with congenital heart diseases (CHD) are one of the leading symptoms that manifest both as a result of hemodynamic overloads during the natural course of the defect or the presence of a congenital arrhythmogenic substrate, and in the postoperative period after surgical correction of CHD, even in individuals who did not have a history of rhythm disturbances. Objective. Assessment of immediate results after various approaches to CHD surgical treatment in adult patients with concomitant arrhythmias. Material and methods. This retrospective study included 378 patients operated between 2011 and 2019 and divided into the following groups: 1st (n = 217) – who had no history of arrhythmias; 2nd (n = 89) – with arrhythmias and underwent isolated correction of the defect (without antiarrhythmic procedure); 3rd (n = 52) – with arrhythmias and who underwent the "Maze" procedure simultaneously with the correction of the defect; 4th (n = 20) with arrhythmias and underwent an antiarrhythmic procedure before the correction of the defect. The primary points were early postoperative mortality and manifestation of arrhythmias at the hospital stage. Secondary points: cardiopulmonary bypass and aortic cross-clamp time, the intensive care unit and hospital staying duration, the frequency of pacemaker implantation and repeated antiarrhythmic procedures, as well as the structure of manifest arrhythmias. Results. The median age in the groups was 52.5 ± 7.4 years for 1st group, 55 ± 9.8 years for 2nd group, 53.2 ± 8.5 years for 3rd group and 55.6 ± 9.4 years for 4th group. Hospital mortality was: 4 (1.8%) in 1st group, 4 (4.5%) in 2nd group, 2 (3.8%) in 3rd group and 0 for 4th group (p2–4 = 0.02). In the early stages after surgery, arrhythmias manifested in 69 (31.8%) cases in 1st group, in 42 (47.2%) – 2nd, in 20 (38.5%) – in 3rd and in 3 (15%) – in group 4th (p1–2 = 0.06, p1–4 = 0.02, p3–4 = 0.01). The smallest number of patients who underwent pacemaker implantation was noted in 1st group and 4th group (5 (2.3%) and 1 (5%) respectively), and the largest in groups 2nd and 3rd (12 (13.5%) and 10 (19.2%), respectively) (p1–2 = 0.003, p1–4 = 0.05, p3–1 = 0.002, p3–4 = 0.01). RFA in the first days after surgery was performed by the subjects of 1st groups, 2nd and 3rd (4 (1.8%), 6 (6,7%) and 3 (5.8%) respectively). Conclusion. Adult patients with CHD who do not have a history of arrhythmias are subject to a high frequency of their development in the early postoperative period after correction of the defect. Simultaneous antiarrhythmic procedure with surgical correction (Maze) does not worsen hospital mortality rates, however, it is associated with a tendency to a higher frequency of pacemaker implantation. The best hospital outcomes after correction of CHD are observed in patients who underwent an antiarrhythmic procedure before surgery.