Background: Simple pulmonary vein (PV) isolation is ineffective in treating patients with persistent atrial fibrillation (AF) and the contributions of atrial regions to the maintenance of persistent AF are not known. This study sought to analyze the preferential anatomical sites where ablation leads to direct termination of AF in persistent AF patients. Methods: A total of 45 patients (36 males, mean age: 55.7 짹 8.8) who were converted to sinus directly during catheter ablation for drug- refractory persistent AF were included. A stepwise ablation approach included circumferential pulmonary vein isolation followed by left atrial and right atrial complex fractionated electrogram (CFAE) guided ablation. Results: AF was terminated to sinus during PV isolation in 18 (40.9%) patients. Seven patients terminated during ablation of left side PVs, 10 patients during right side PVs and 1 patient during box isolation. Remaining 26 patients underwent CFAE mapping and CFAE guided ablation after PV isolation. Seventeen patients showed AF termination during left atrial CFAE ablation, six patients during right atrial CFAE ablation, one patient during right atrial CFAE mapping and one during cavotricuspid isthmus ablation. The most frequent termination sites of left atrial CFAE area were the left inter-atrial septum (n=8) followed by anterior wall at the base of the left atrial appendage (n=5), the mitral annulus (n=2), perimitral posterior isthmus (n=1), posterior wall (n=1). Conclusions: The preferential sites of AF termination were around the PVs, the left inter-atrial septum, and the anterior wall of the left atrium. These sites might be the critical atrial structures in the maintenance of AF.