Introduction: This study aims to understand the usefulness of a novel noninvasive 3-dimensional electrocardiography system (3D-ECG) in the diagnosis of prior myocardial infarction. Material and methods: 212 patients with more than 1 month history of acute myocardial infarction were selected as prior myocardial infarction group (PMI). 88 patients without myocardial infarction were selected as control group (NPMI). Electrocardiograph and 3D-ECG were applied on all patients in order. Results: Comparison between 3D-ECG and ECG was accomplished in 212 prior myocardial patients and 88 non myocardial patients. 3D-ECG correctly diagnosed prior myocardial infarction in 210 of 212 (99%)PMI and non myocardial infarction in 84 of 88 (95%) NPMI, while ECG diagnosed prior myocardial infarction in 132 of 212 (62%) PMI and non myocardial infarction in 84 of 88 (95%) NPMI. 3D-ECG misdiagnosed prior myocardial infarction in 2 of 212 (0.9%) PMI and non myocardial infarction in 4 of 88 (4.5%) NPMI while ECG misdiagnosed prior myocardial infarction in 80 of 212 (37.7%) PMI and non myocardial infarction in 84 of 88 (4.5%) NPMI. Discussion: The study shows a high success rate of 3D-ECG in accurately diagnosing the prior myocardial infarction comparing with ECG and its application to diagnose prior myocardial infarction is under the way.