PURPOSE:Coronary artery calcium (CAC) is a specific indicator of and an independent risk factor for atherosclerosis; however, calcium scoring may miss noncalcified plaques, which may have clinical importance. The aim of this study was both to identify the presence and extent of coronary plaques during computed tomography coronary angiography (CTCA) in patients with a zero CAC score and to evaluate the effect of risk factors and symptom status on the presence of noncalcified plaques. MATERIALS AND METHODS:In this retrospective study, we analyzed the cases of 842 consecutive patients between October 2006 and November 2011. Of these patients, we included 357 with a zero calcium score in the study. Information regarding patient age, sex, coronary risk factors, and symptom status were recorded. Coronary calcium-scoring scans were followed by CTCA. The calcium scores were calculated, and the presence of noncalcified plaques and significant stenoses (>50% of vessel diameter) was evaluated. RESULTS:Of the 357 patients with a zero calcium score, 37 (10.36%) had atherosclerotic plaques; 9 patients (2.52%) had significant coronary stenosis. Among coronary risk factors, only diabetes mellitus was significantly correlated with any risk factors (presence of atherosclerosis and obstructive coronary artery disease; P = .030 and .013, respectively). CONCLUSION:Although CAC scoring is a safe and a reliable test to exclude obstructive coronary artery disease, the absence of CAC does not definitively exclude the presence of atherosclerosis. CTCA is a more appropriate method for determining the atheroma burden.