Aim. To estimate the influence of short-term omega-3 polyunsaturated fatty acids (PUFA) treatment on the development of new cases of atrial fibrillation (AF) in patients with coronary artery disease after coronary artery bypass grafting (CABG) with the detection of indicators of inflammation, oxidative stress, myocardial injury or dysfunction. Material and methods. The patients did not receive statins at the stage of out-patient treatment. Interleukin (IL)-6, IL-8, IL-10, C-reactive protein (CRP), fibrinogen, troponin, NT-proBNP, superoxide dismutase (SOD), myeloperoxidase (MPO) levels were measured on admission and 3.6±1.3 days after CABG. All the patients were divided into two groups: group 1 comprised patients who did not receive omega-3 PUFA (51 patients, 86.3% males, mean age 62.8+4.0), 2 group included patients who received PUFA (51 patients, 90.2% males, mean age 62.1±4.0 years) 5 days (mean) before CABG at an average dose 2 g per day and for 3 weeks after CABG at an average dose 1 g per day. Results. Postoperative AF more often occurred in group 1 (41.2% vs 23.5%; p=0.04 ( mean 4.8±3.0 days). The patients of group 1 more often had FC-III angina pectoris (60.8% vs 51.0%, p=0.04), whereas patients of group 2 more often had the history of myocardial infarction (78.4% vs 58.8%, p=0.03) and respiratory pathology (23.5% vs 2.0%, p=0.0009). According to univariate regression analysis, omega-3 PUFA intake was associated with a decrease of new episodes of AF at the early postoperative period (odds ratio (OR) 0.66; 95% confidence interval (CI) 0.43-0.9; p=0.04). IL-6 levels were significantly higher in pre- and postoperative periods in patients of group 1 (34.8±25.5 pg/ml vs 2.9±2.5 pg/ml, p<0.0001; 54.6±44.9 pg/ml vs 39.5±29.7 pg/ml, p=0.04, respectively). Before CABG, SOD levels in both groups were higher than normal (group 1 - 3478.6±2365.7 units/g vs group 2 - 2893.4±2365.7 units/g, p>0.05). After CABG, SOD levels became lower in both groups but remained significantly higher in group 1 (2311.8±1371.6 units/g vs 662.5±572.4 units/g, р<0.0001). MPO after CABG was insignificantly raised in group 1 (before CABG - 176.8±83.8 mg/l, after CABG - 212.5±131.8 mg/l) and lowered in patients with omega-3 PUFA intake (280.4±202.1 before and 235.3±147.6 after CABG). Conclusions. The study showed that omega-3 PUFA intake in perioperative period of CABG leads to a significant decrease in occurrence of new AF cases. The patients who received omega-3 had lower IL-6 levels as a proinflammatory factor and SOD level as a marker of oxidative stress.