INTRODUCTION: There have been rare case reports of damage to adjacent coronary arteries by screw-in pacemaker and implantable cardioverter-defibrillator (ICD) leads. Our aim was to assess the proximity of pacemaker and ICD leads to the major coronary anatomy using cardiac computed tomography (CT). METHODS: Cardiac CT images were retrospectively analyzed to assess the spatial relationship of device lead tips to the major coronary anatomy. RESULTS: Fifty-two right ventricular (RV) leads (17 apical, 35 nonapical) and 35 right atrial (RA) leads were assessed. Leads on the RV antero-septal junction (20 of 52) were close (median 4.7 mm) to, and orientated toward, the left anterior descending (LAD) coronary artery. RA leads in the anterior (26 of 35) and lateral (seven of 35) walls of the RA appendage were not close to (16.9 +/- 7.7 mm and 18.9 +/- 12.4 mm, respectively) and directed away from the right coronary artery. However, an RA lead adjacent to the superior border of the tricuspid valve was 4.3 mm from the right coronary artery and an RA lead on the medial wall of the RA appendage was 1.6 mm away from the aorta. An RV pacemaker lead in the lateral wall of the RV inlet was 3.4 mm from the right coronary artery. CONCLUSIONS: In our cohort, a majority of RV leads were on the antero-septal junction and close to the overlying LAD coronary artery. RA leads adjacent to the tricuspid valve or on the medial RA appendage were in close proximity to the right coronary artery and aorta, respectively.