The improved technology of multi-slice cardiac CT angiography (CTA) has enabled production of high quality images of the coronary arteries. The sensitivity and specificity of the test in identifying patients with obstructive coronary lesions in 64-slice and later generations of scanners is high. To enable effective use of CTA in the clinical setting, a better understanding of this technology, particularly in comparison to invasive coronary angiography, is needed. In this article we discuss the characteristics of CTA in comparison to invasive coronary angiography and discuss the role of CTA in the diagnosis of coronary artery disease (CAD). Newer CTA scanners and individualized scanning protocols can minimize radiation exposure from CTA. CTA can provide more information than invasive coronary angiography on the type and burden of atherosclerotic plaque in the coronary tree. CTA is most useful in those at intermediate risk of CAD.