BACKGROUND: Recently anterior wall linear ablation is tried for the mitral isthmus dependent atrial flutter. AIM: To prevent collateral damage, We studied the relationship of coronary artery and anterior wall. Methods: A total of 91 patients with non-paroxysmal atrial fibrillation (60 men, 31 women; age 60짹12 years) who underwent catheter ablation were enrolled. We measured the shortest distances between anterior wall and left main (LM), LM bifurcation site and left circumflex (LCX) artery using 3-D carto merge system and 64 channel cardiac multidetector computed tomograohy (MDCT) respectively. Anterior wall thickness of aortic side and LA appendageal side and the distance from roof line to mitral annulus were measured. Results: There are three patterns of anatomic relationship between anterior wall and coronary arteries shown in Fig. 1. In type I (51 case, 56%), the LCX is the shortest artery from anterior wall (3.709짹1.604 mm), in type II (30 case, 32%), the LM bifurcation site is the shortest (6.369짹3.122 mm), and in type III (10 case, 10%), the LM is the shortest distance coronary artery (7.117짹3.070 mm). Aortic side of anterior wall is slightly thicker and significantly longer than LA appendageal side of anterior wall (2.886짹0.9376 mm vs.1.501짹0.5323 mm p<0.0001; 45.0짹7.0 mm vs. 28.1 짹 5.3 mm, p<0.0001, respectively). Conclusions: The catheter ablation applied to left anterior wall has low risk of damage to coronary artery, but the optimal site of anterior line should be determined individually considering coronary artery anatomic diversity.