PURPOSE The purpose of this study is (a) to investigate the prevalence and plaque characteristics of coronary atherosclerosis and (b) to evaluate predictors for the risk stratification of coronary atherosclerosis using by coronary CT angiography (CCTA) in young adults. METHOD AND MATERIALS Among the registry of 15355 patients who underwent CCTA between January 2006 and December 2008 in our institute, we retrospectively enrolled 2263 subjects under the age of 45 (1428 men, 835 women; mean age 39.9짹 3.7 years). The plaque burden (number of diseased coronary segments), severity of stenosis, plaques characteristics, and coronary artery calcium score (CACS) were assessed by MDCT. We also evaluated conventional risk factors to assess predictors for the presence of coronary atherosclerosis revealed by CCTA. RESULTS CCTA revealed atherosclerotic plaques in 307 segments from 223(9.8%) subjects(mean 1.38 짹 0.81 segments/subject; range 1 to 6). Twenty one(0.9%) subjects had a significant(��� 50%) stenosis on CCTA, and of those, 3(14.3%) of them had severe(��� 75%) stenosis. Most of them(89.5%) had single-vessel disease, and most of the significant lesions(78.9%) were located in the left anterior descending coronary artery. Noncalcified plaques(50.5%) emerged as the most frequent type of atherosclerotic plaque. Mixed plaque and calcified plaque were found in 29.3% and 20.2%. CACS of study population was 1.83짹16.2. Only eleven patient had calcium scores above 100 Agatston U, however, 2151(95.1%) had CACS=0. Eleven(0.5%) subjects had noncalcified plaque with significant stenosis. DM, hypertension, male gender, and age were independent predictors for presence of any plaque. The incidence of atherosclerotic plaques regardless of plaque composition increased with age(p<.05). In contrast, significant stenosis and high calcium scoring was found to have no significant linear association with age. DM, hypertension, amount of smoking(total pack-year) and male gender were independent risk factors for noncalcified plaque. CONCLUSION Even though the prevalence of coronary atherosclerosis in young adults is low, noncalcified plaque is very common. DM, hypertension, male gender and age are significant predictors for presence of coronary atherosclerosis in young adults.