Coronary artery aneurysm formation is an uncommon finding after coronary stent implantation and is possibly related to deep vessel injury, plaque regression and positive remodeling. We report herein a 31-year-old patient who developed an aneurysm of a coronary artery four months after successful stent implantation to relieve a chronic, totally occluded lesion. The aneurysm occurred within the stented segment of the artery. Intravascular ultrasound image revealed good stent apposition without visible vessel dissection. The aneurysm regressed spontaneously after the ensuing five months.