Purpose: The purpose of the present study is to investigate whether daily administration of 20mg of rosuvastatin in combination with 10mg of ezetimibe could make more favorable alteration in plaque composition than that of rosuvastatin 20mg alone. Methods: Thirty-four stable and unstable angina pectoris patients not on statin therapy were enrolled. The culprit lesions were treated with standard PCI technique. The patients were randomly assigned to either 20mg of rosuvastatin with 10mg ezetimibe (group A, n=17) or 20mg of rosuvastatin alone (group B, n=17). Non-significant coronary lesions (group A n=35, group B n=31) were assessed with virtual histology (VH) study at baseline and 12-month follow-up. Each plaque components (fibrotic, fibrofatty, dense calcium and necrotic core) were analyzed by volumetric methods. Results: LDL cholesterol was significantly reduced in both groups (162짹23mg/dl to 76짹9mg/dl, p=0.015; 153짹19mg/dl to 66짹8mg/dl, p=0.004), however there was no significant difference in 12 month follow-up LDL cholesterol between two groups (76짹9mg/dl vs. 66짹8mg/dl, p=0.234). In overall patients, necrotic core was significantly reduced (16.1짹3.1 to 12.3짹1.7mm³, p=0.023) and fibrotic plaque was increased (26.3짹8.8 to 33.5짹7.6mm³, p=0.016) after 1 year lipid lowering treatment. There were no significant changes in fibrofatty plaque and dense calcium in both groups (13.1짹4.7 to 11.9짹3.6mm³, p=0.190; 11.6짹4.5 to 12.1짹5.2mm³, p=0.405). However there was no significant difference in the reduction of necrotic core (24.5% vs. 23.7%, p=0.690) and in the increment of fibtrotic plaque (26.1% vs. 28.9%, p=0.351) between two groups. Conclusions: Lipid lowering therapy either with rosuvastatin 20mg and ezetimibe 10mg or with rosuvastatin 20mg alone may be associated with significant reduction in necrotic core and increment in fibrotic plaque volume in overall patients. However additional treatment with ezetimibe 10mg failed to achieve more favorable alteration in plaque composition than rosuvastatin 20mg alone.