Introduction; Coronary artery aneurysm(CAA) after drug-eluting stent(DES) implantation is rare complication and has not been evaluated sufficiently in real-world practice. Methods and Resuts; We evaluated the incidence, clinical characteristics and long-term prognosis of CAA after DES implantation in 1179 patients (1465 lesions;sirolimus-eluting stent in 921 lesions and paclitaxel-eluting stent in 553 lesions) in whom follow-up angiography was performed at at least 6-month. CAA occurred in 34 patients with 36 lesions(2.46% overall, 23 lesions [2.52%] in sirolimus-eluting stents and 13 lesions[2.5%] in paclitaxel-eluting stents, P=0.64); the incidence was 50.0%(18/36) in chronic total occlusions, and 27.8%(10/36)after primary stenting in acute myocardial infarction. The incidence of aneurysm types was 50%(18/36) for saccular form, 13.9%(5/36) for fusiform, and 36.1%(13/36) for microform. Independent predictors of CAA were chronic total occlusion lesions and acute myocardial infarction. Except for 1 late stent thrombosis in microform aneurysm after discontinuation of dual antiplatelet therapy and 1 late stent thrombosis associated with concomittent stent fracture, there were no major adverse cardiac events during a mean 28 month follow-up. Their long-term clinical course were variable: among 15 cases with follow-up angiogram after detection of CAA, 2 case showed stent thrombosis, 3 cases showed spontaneous resolution, and 1 case showed enlargement of CAA, no interval change in 7 cases, 1 case underwent graft stent implantation and 1 micro-CAA conglomerated into saccular form. Conclusions; CAA occurs in about 2~3% of cases after DES implantation. The predictors of CAA are chronic total occlusion lesions and primary stenting in myocardial infarction. CAA after DES implantation seems to be not associated with major adverse cardiac events during a subsequent 28-month follow-up. Long-term follow-up study is required to guideline the duration of dual antiplatelet therapy in this patients.