Iterative reconstruction techniques for coronary CT angiography have been introduced as an alternative for traditional filter back projection (FBP) to reduce image noise, allowing improved image quality and a potential for dose reduction. However, the impact of iterative reconstruction on the coronary artery calcium score is not fully known. In 112 consecutive stable patients with suspected coronary artery disease, the coronary calcium scores were assessed. Comparisons were made between the Agatston, volume and mass scores obtained with traditional FBP, and by using adaptive statistical iterative reconstruction (ASIR). A significant reduction of the Agatston score, volume score and mass score was observed for ASIR when compared to FBP, with median differences of resp. 26, 5 mm(3) and 1 mg. Using the ASIR reconstruction, the number of patients with a calcium score of zero increased by 13 %. Iterative CT reconstruction significantly reduces the Agatston, volume and mass scores. Since the calcium score is used as a prognostic tool for coronary artery disease, caution must be taken when using iterative reconstruction.