Our aim was to study the predictive value of NT proBNP regarding the risk of AF and clinical features in acute phase of ST-segment elevation MI (STEMI). Methods. We examined 56 patients with STEMI and AF who did undergo the primary PCI. 35 (62.5 %) of patients had the new-onset AF (group 1), 21 (37.5 %) had pre-existing AF (group 2). Control group consisted of 60 patients with STEMI without AF (group 3). Results. Group 3 patients were more likely to be smokers than patients in group 2. They had lower admission heart rate and glycemia, lower NT proBNP, higher hemoglobin and ejection fraction. Patients in group 1 were more likely to have anterior MI, left anterior descending artery as an infarction-related artery (IRA) and adverse cardiac events (MACEs). Patients in group 2 had higher left atrium end-systolic diameter and were more likely to have three-vessel injury. NT proBNP correlated positively with age, admission glycemia, mean PA pressure and negatively – with GFR. ROC analysis had shown the cut-off point of NT proBNP level for prediction of AF was >1050 pg/ml. Cut-off point for prediction of the risk of MACE in STEMI complicated with AF was >2189 pg/ml. Discussion. It was shown that NT proBNP is higher in STEMI patients who have AF. Increased NT proBNP is associated with the risk of adverse events in acute STEMI phase. NT proBNP level can be utilized as AF predictor in STEMI patients and as predictor of MACEs in patients with STEMI and AF.