The electrocardiogram (ECG) is an important tool in ST-segment elevation myocardial infarction (STEMI) for identifying the affected wall. In inferior wall STEMI, both the right coronary artery (RCA) and the left circumflex artery (LCxA) may be responsible for the event, and identification of the culprit artery becomes possible through the application of electrocardiographic criteria. We report two cases that illustrate the challenges and overlaps of certain ECG patterns and their angiographic correlations. In case 1, the first ECG showed ST-segment elevation in D2, D3 and aVF, with ST-segment elevation in D1 and ST-segment depression in aVR. In the second ECG, ST-segment elevation was evident in inferior wall, with higher elevation in D3 and with ST-segment depression in D1, aVL and V2. Coronary angiography showed an occluded LCxA with a negative image suggestive of thrombus, and chronic total occlusion of the RCA. In case 2, the ECG showed ST elevation in D3 and aVF, and ST depression in aVL, V2, V3 and V4. On a new ECG, ST-segment elevation was observed in D1, D2 and aVF, and ST-segment depression was observed in V2 and aVR. In coronary angiography, ostial chronic occlusion of the RCA was visualized, in addition to subocclusive stenosis in the second obtuse marginal branch and in the LCxA. The electrocardiographic findings of both cases highlight the importance of well-established criteria that contribute to identifying the occluded artery in inferior STEMI.