As an important tool for diagnosing acute coronary syndrome and stable angina, coronary CT angiography has been increasingly being performed in patients presenting with atypical chest pain. In order to help treating patients more efficiently, it is crucial for radiologists to have a comprehensive understanding about mechanisms and clinical aspects as well as CT findings of coronary atherosclerosis per se. A thorough understanding and optimal performance of coronary CT angiography may lead to reduction of unjustified downstream testing. This article provides a clinical and radiological overview of coronary atherosclerosis, and a practical guideline about how to interpret degree of stenosis on coronary CT angiography.