Objectives : Lipid-lowering therapy with statin may reduce the risk of cardiovascular events. Our study aim was to assess a dose dependent statin effects by using a cardiac MRI for measurement of myocardial infarction size. Method : We evaluated the cardiac MRI findings of 44 consecutive patients with acute myocardial infarction who underwent a percutaneous coronary intervention in Saint Carollo hospital. Initial and follow-up cardiac MRI was checked at 1 week and 12weeks after revascularization and high dose lipid-lowering therapy (Rosuvastatin 40mg, Group I, n=24) or low dose (Rosuvastatin 5mg, Group II, n=20). In MRI analysis, we evaluated the changes of microvascular obstruction (MVO, first-pass enhancement) and infarct size (delayed enhancement) that was expressed as a percentage of left ventricle area. Results : There were no differences of baseline characteristics between groups. The mean follow-up periods of cardiac MRI was 12.9짹1.2 weeks. The changes of MVO in 2 groups showed a tendency of decreasing size, but there was no significant difference (-1.90짹1.49 vs. -1.52짹1.83, p=0.455). However the changes of infarct size in Group II was larger than Group I (0.45짹2.4 vs 2.27짹3.24, p=0.013). Conclusions : Compared with a low dose, high dose treatment of rosuvastatin significantly reduces infarct size after revascularization in AMI.