PURPOSE: The anatomy of the left atrium (LA) and the pulmonary veins (PVs) is important in planning and performing successful electrophysiologic ablation (EPA) for atrial fibrillation (Afib) patients. The authors estimated the findings of LA and PVs of Afib patients by MDCT, and compared these with the findings of LA and PVs of the non-Afib group using coronary CT angiography (CCTA). MATERIALS AND METHODS: From September, 2009 to February, 2010, 91 Afib patients underwent PVCT (male: female = 72:19, mean age = 55.0-years-old) before EPA. At same time, 90 patients underwent CCTA (male: female = 73:17, mean age = 59.1-years-old). Two radiologists reviewed and analyzed all axial and 3D images of LA and PVs retrospectively with consensus. RESULTS: The average LA volumes of the Afib group(100.49 mm3) was larger than that of the non-Afib group (78.38 mm3) (p<0.05). The average lengths of the LA right wall in the Afib group (40.25 mm) was longer than that of the non-Afib group (37.3 mm) (p<0.05). The average distances between the PV ostium and first segmental bifurcation of the Lt superior PV (LSPV) and the RSPV were shorter in the Afib group (LSPV, 19.38 mm; RSPV, 11.49 mm) than in the non-Afib group (LSPV, 23.23 mm; RSPV, 14.25 mm) (p<0.05). There were higher incidences of anomalous branches such as ostial, accessory branches, or common ostia in the Afib group versus the non-Afib group (p<0.05). CONCLUSION: In Afib group, variable parameters of LA and PVs were obtained and estimated by MDCT, and there was statistically significant difference in the parameters of LA and PVs between Afib and non-Afib groups.