Background: Coronary angiography is an invasive diagnostic procedure, which could induce several procedure related complications. The aim of study was detect the incidence of micro-embolic cerebral infarction by diffusion-weighted (DW) magnetic resonance imaging (MRI) after coronary angiography (CAG). Methods: Two hundred eight patients, who were performed DW-MRI for the preparation of planned coronary artery bypass surgery (CABG), were retrospectively enrolled in this study. All patients had no evidence of recent cerebral infarction. DW-MRI should be performed within 36 hours after diagnostic CAG. The clinical and angiographic characteristics were analyzed according to the existence of embolic infarction: group 1 – event group, group 2 – no event group. Results: Twenty patients (9.6%) had newly developed micro-embolic infarction in the DW-MRI after diagnostic CAG. These patients had no symptomatic event. The left ventricular ejection fraction (LVEF) was lower in group 1 (45.8짹8.5%, group 2: 51.9짹13.2%; p=0.046). Age, underlying atrial fibrillation and the extent of coronary disease did not effect on the event. Conclusions: The incidence of asymptomatic micro-embolic cerebral infarction after diagnostic coronary angiography was relatively high. It well may be substantially higher than expected; a more accurate evaluation of the true incidence would require a significantly larger study population. Careful and gentle technique should be needed to prevent the complications after diagnostic coronary angiography.