Noninvasive identification of nonculprit lesions could improve preventive strategies for acute myocardial infarction (AMI). We assessed the morphology, composition, and spatial distribution of nonculprit coronary plaques in patients with AMI using computed tomographic angiography (CTA). A total of 64 patients with AMI underwent 64-slice CTA within 2 weeks after admission, and 162 symptomatic patients with stable angina pectoris (SAP) underwent CTA and stress myocardial perfusion imaging (MPI). Of these 226 patients, 16 were excluded from the analysis because of image artifacts. The mean number of nonculprit plaques per patient was 5.0 ± 2.6 in the AMI group (n = 60), 4.2 ± 2.6 in the SAP group with abnormal MPI findings (n = 67), and 1.1 ± 1.3 in the SAP group with normal MPI findings (n = 83; p <0.01). Positive remodeling and low-attenuation plaques (<30 Hounsfield units) were more frequently observed in the AMI group (1.9 ± 1.8) than in the SAP groups (0.6 ± 0.9 with abnormal MPI findings and 0.2 ± 0.4 with normal MPI findings; p <0.01). Within the AMI group, positive remodeling and low-attenuation plaques were present significantly more frequently in patients with metabolic syndrome than in those without (2.6 ± 2.2 vs 1.4 ± 1.4; p = 0.03) and was significantly more frequently distributed in the proximal segments of the left anterior descending artery (p <0.01). In conclusion, 64-slice CTA could provide promising information for preventive strategies by identifying nonculprit plaque morphology and zones at high risk of future events.