Background: Reperfusion therapy basically aims to restore full antegrade flow in the infarct-related epicardial coronary artery. The modified Selvester QRS score, basically developed to estimate infarct size, was used with good predictive value to predict ST-resolution in acute myocardial infarction (AMI) treated with fibrinolysis. However, little data are available about its role in predicting reperfusion in ST-segment myocardial infarction (STEMI) patients undergoing primary percutaneous coronary interventions (PCI). Objectives: The aim of this work was to examine the value of modified Selvester QRS score in predicting ST-segment resolution in patients with first acute STEMI after thrombolytic therapy or primary PCI. Methods: Sixty patients with acute STEMI were enrolled in the study, 56 males and 4 females; and their mean age was 56.4±8.4 years. We excluded patients with bundle branch block, paced rhythm, left fascicle block, ECG signs of ventricular hypertrophy, cardiogenic shock and prior STEMI. All patients were submitted to full history taken and clinical examination, admission 12-leads electrocardiography (ECG) with estimation of modified Selvester QRS score and sum of ST-elevation, another ECG after 90 minutes of thrombolysis with estimation of the sum of ST-elevation and STresolution, cardiac enzymes, thrombolysis for 45 patients and primary PCI for 15 patients, echocardiographic assessment with measuring of left ventricular ejection fraction (EF) and wall motion score index (WMSI), and coronary angiography. Results: Population characteristics and risk factors for coronary artery disease (CAD) were comparable between the two groups. In patients with QRS score > 4, time to admission was significantly higher, EF was significantly lower, WMSI was significantly higher, number of patients with no STsegment resolution was significantly lower, number of patients with myocardial blush grade (MBG) 1 was significantly higher, number of patients with MBG 3 was significantly lower, and number of patients with three-vessel disease was significantly higher. Sensitivity of QRS score ≤ 4 in predicting ST-segment resolution ≥ 50 % was 59.3%, specificity was 100 %, positive predictive value was 62.1 %, negative predictive value was 86 %, and overall accuracy was 75.6 %. There was a highly significant negative correlation between ST-segment resolution and QRS score (r = - 0.483, p = 0.00078). Conclusion: Selvester QRS scoring system is regaining its clinical value in patients with first STEMI. It can provide valuable information as regard area of myocardium at risk, prediction of residual left ventricular function, making treatment decisions. Though somewhat difficult, it is worthy to calculate QRS score from admission ECG in every patient presenting with STEMI. In patients who are controversial as regard thrombolytic therapy, QRS score could help in determining those who will get benefit from such therapy