Left main coronary artery (LMCA) aneurysm is a rare coronary abnormality defined as localized coronary artery dilatations>1.5 to 2 times the diameter of the adjacent segments. The incidence of coronary artery aneurysm varies between 0.15% and 4.9%. It can be recognized by coronary angiography or multidetector computed tomography. Here, we present three cases of LMCA aneuryms, of one which firstly diagnosed by multidetected computed tomography.