Accessory pathways can lie near or within the coronary sinus (CS). Radiofrequency catheter ablation of accessory pathways is a well-established treatment option, but this procedure can cause damage to adjacent coronary arteries.The purpose of this study was to evaluate the anatomic relationship between the coronary arteries and the CS.Retrospective data of patients who underwent catheter ablation of supraventricular tachycardia between June 2011 and August 2013 was reviewed. In addition, detailed analysis of coronary computed tomographic angiography (CTA) data from 50 patients was performed.Between June 2011 and August 2013, 427 patients underwent catheter ablation of supraventricular tachycardia, of whom 105 (age 28 ± 17 years, 60% male) had accessory pathway-mediated tachycardia. Of these, 23 patients had accessory pathways near the CS, and 60% (N = 14) underwent concurrent coronary angiography. In 4 patients, the posterolateral (inferolateral) branch (PLA) of the right coronary artery was in close proximity to the CS, and 2 patients (18%) had stenosis of the PLA at the site of ablation. On CTA at their closest proximity, the PLA was 1.9 ± 1.3 mm and the left circumflex artery (LCx) was 2.0 ± 0.8 mm from the body of the CS, in right and left coronary artery-dominant patients, respectively. CS ostium and PLA were 3.6 ± 1.9 mm apart. In left-dominant patients, LCx and CS ostium were 3.8 ± 1.2 mm apart.The PLA and LCx are in close proximity to the anteroinferior aspect of the CS ostium and proximal CS. The relationship of the CS and coronary arteries should be evaluated before ablation at these sites.