A prospective study was conducted to determine the diagnostic accuracy of Q wave on ECG in predicting the non-viable myocardium in patients with myocardial infarction, considering SPECT as the gold standard in the Department of Nuclear Cardiology, Ch. Pervaiz Elahi Institute of Cardiology (CPEIC), Multan, from June 2022 to June 2023. A total of 414 patients with myocardial infarction were included in the study. Demographic and clinical data such as age, gender, smoking history, diabetes, and hypertension were collected. Before the SPECT scan, 12 lead ECG was done in all patients to determine the pathologic Q wave. Pathologic Q-wave on ECG was found in 252 (60.87%) and not in 162 (39.13%) patients. Non-viable myocardium on SPECT was found in 231 (55.80%) and not in 183 (44.20%) patients. Pathologic Q-wave was 68.80% sensitive and 49.20% specific, with 63.10% PPV and 55.60% NPV compared to SPECT. This difference was statistically significant (P<0.001). Development of pathologic Q wave on ECG was significantly associated with male gender (P =0.006), hypertension (P=0.008), and smoking (P=0.002). In conclusion, pathologic Q wave on ECG is a reliable tool for predicting non-viable myocardium in CAD patients.