PURPOSE To evaluate the characteristic imaging findings on ECG-gated MDCT in patients with acute non-ST elevated myocardial infarction (NSTEMI). METHOD AND MATERIALS Among the consecutive 213 patients with acute chest pain who underwent ECG-gated 64-slice MDCT, all patients were immediately performed MDCT scanning after checking ECG and clinical status at emergency department. We retrospectively reviewed in 15 patients (M:F=13:2; 63.5 짹 8.7 yrs) with acute NSTEMI finally revealed by ECG, cardiac enzymes, and conventional angiography. We evaluated MDCT findings in terms with plaque composition and density, lesion length, remodeling index (RI), and enhancement of vessel wall. We also assessed density of infracted and remote normal myocardium and regional wall motion abnormality (RWMA) and associated perfusion defect (PD) on corresponding vascular territory. RESULTS Initial ECG abnormality showed in 4 patients with ST-depression and 5 patients with T-inversion. Initial elevation of cardiac enzyme was seen in only 2 patients, even though all patients had elevated cardiac enzyme on follow-up exam after MDCT. All patients showed intraluminal filling defect within coronary lumen. Imaging findings of culprit coronary lesion on MDCT of inpatient with acute NSTEMI were as follows: plaque composition (noncalcified: mixed = 13:2), plaque density (32짹12 HU), lesion length (8.2짹6.9 mm), RI (1.46짹0.16), type of enhancement at vessel wall (partial slight (n=5); concentric slight (n=6); concentric strong (n=4)). The density of myocardium at infarct area and remote normal area is 38짹19 and 115짹15 HU, respectively. RWMA and associated PD on corresponding vascular territory of culprit lesion showed 13 in 15 patients (86%). CONCLUSION The characteristic imaging findings on ECG-gated MDCT in patients with acute NSTEMI is discrete intraluminal filling defect with density of thrombus, severe positive remodeling, and enhancement of vessel wall. RWMA and associated PD frequently showed at corresponding vascular territory of culprit lesion.