BACKGROUND Although low voltage zones (LVZs) in the left atrium (LA) are seen as arrhythmogenic substrate in some patients with atrial fibrillation (AF), pathophysiologic factors responsible for LVZ formation remain unclear. OBJECTIVE To elucidate the anatomical relation between the LA and ascending aorta responsible for remodeling of the anterior LA wall. METHODS We assessed the relation between existence of LVZs on the anterior LA wall and measurements taken on 3-dimensional computed tomography images obtained from 102 patients who underwent AF ablation. RESULTS Twenty-nine patients (28%) had LVZs >1.0 cm2 on the LA wall at the LA-ascending aorta contact area (LVZ Group); no LVZs were seen in the other 73 patients (No LVZ Group). In the LVZ Group (vs. No LVZ Group), the aorta-LA angle was smaller (21.0±7.7° vs. 24.9±7.1°, P = 0.015), the aorta-left ventricle (LV) angle was greater (131.3±8.8° vs. 126.0±7.9°; P = 0.005), non-coronary cusp (NCC) diameter was greater (20.4±2.2 mm vs. 19.3±2.5 mm; P = 0.036), and the NCC was closer to the anterior LA wall (2.29±0.68 mm vs. 2.76±0.79 mm; P = 0.006). The aorta-LA angle correlated positively with patients’ body mass index (BMI) and negatively with body weight and BMI. CONCLUSION Deviation of the ascending aorta course and distention of the NCC appear to be related to the development of LA anterior wall LVZs at the LA-ascending aorta contact area. Mechanical pressure exerted by extracardiac structures on the LA along with limited thoracic space may contribute to the development of LVZs associated with AF.