Pulmonary vein isolation using either radiofrequency or cryoballoon ablation has emerged as a widely used treatment modality in patients with paroxysmal atrial fibrillation. In our first single-center study, we followed 98 patients with symptomatic, drug-refractory paroxysmal atrial fibrillation who underwent pulmonary vein isolation for the first time between September 2012 and December 2013 at the Gottsegen National Cardiovascular Center using the second-generation cryoballoon catheter or the contact force sensing radiofrequency catheter. Both ablation techniques were found to be safe, with the cryoballoon procedure being significantly shorter. Late pulmonary vein reconnection patterns around the pulmonary veins show variations after different ablation methods. At the 24-month follow-up, the clinical success rate was comparable between the two ablation techniques. Therefore, in patients with paroxysmal atrial fibrillation, both ablation techniques can be widely used with safety and high clinical efficacy. Secondly, we prospectively investigated the incidence of iatrogenic atrial septal defects and cerebrovascular events associated with transseptal puncture during atrial fibrillation ablation. Our study included 94 patients with paroxysmal atrial fibrillation who underwent cryoballoon or radiofrequency ablation (single or double transseptal puncture) for the first time between July 2014 and September 2016. Transesophageal echocardiography was performed to confirm atrial septal defect before the procedure and assess iatrogenic atrial septal defect at the 3- and 12-month follow-up. This study was the first to make the following findings. The incidence of iatrogenic atrial septal defects was moderately high 3 months after atrial fibrillation ablation, but the ablation technique did not significantly affect its incidence. After radiofrequency ablation, the iatrogenic atrial septal defect incidence was not influenced by the single or double transseptal puncture technique. Finally, iatrogenic atrial septal defects showed a high spontaneous closure rate at 12-months in both ablation groups.