BACKGROUND Since pulmonary vein isolation is increasingly used to treat atrial fibrillation(AF), the procedure has potential risk of pulmonary vein(PV) stenosis. The purpose of this study is to investigate the incidence, clinical and anatomical characteristics of PV stenosis identified by reconstructed three-dimensional computed tomograpgy (3-D CT) after ablation for AF. METHODS In our series of 190 patients with redo catheter ablation(CA) of AF, 27 consecutive patients (13.7%) with the presence of PV stenosis after ablation of AF were studied. We classified study population into three groups according to the degree of stenosis as follows: mild (50%), moderate (50-75%),or severe (>75%). RESULTS In 27 patients (mean age 54짹11 years), 13 paroxysmal AF and 14 non paroxysmal AF were identified. Twenty (81.5%) patients underwent a 2nd repeat procedure, and 3rd and 4th and 5th repeat procedure was performed in 4 (14.8%), 2 (7.4%), and 1 (3.7%), respectively. Mean time interval to CT was 22짹20 months. Mild PV stenosis was observed in 21 (77.8%), moderate stenosis in 3 (11.1%), and severe stenosis in 3 patients (11.1%). The complete obliteration of PV was identified in 2 patients. Stent implantation was performed in 2 of 3 severe PV stenosis patients. PV stenosis was commonly developed at a single PV, especially left inferior or right inferior PV, in 18 of 27 patients (66.7%) and mostly asymptomatic. Nine patients had more one PV stenosis. In 1 patients, stenosis was observed in 3 PVs. The majority of the PV stenosis showed a discrete pattern, only one mild stenosis was diffuse pattern. The first ablation methods of PV isolation was circumferential antral ablation in 19 (70.4%), segmental ablation in 3 (11.1%), focal ablation in 2 (7.4%), and box isolation in 1 patient (3.7%). In 8 patients (42.1%), PV stenosis occurred after ipsilateral ostial and carina ablation of affected PV. There were no significant differences in LA diameter, LA volume and left ventricular ejection fraction (45.3짹7.2 mm vs 41.1짹5.9 mm, P=0.35, 112.4짹29.9 cm3 vs 99.8짹 28.2 cm3, P=0.29, 54.8짹10.1 % vs 52.8짹8.1 %, P=0.49, respectively) between those before and after PV stenosis. CONCLUSIONS Asymptomatic PV stenosis was not uncommon, which was frequently developed at single PV after ostial and carina ablation. Moderate to severe PV stenosis is a complication with decreasing incidence but,it is the threatening risk of catheter ablation for AF. The result suggested that precise 3-D mapping and careful ablation technique could minimize PV stenosis.