Objectives: The presence of Q waves on the electrocardiogram (ECG) underestimates viability in chronic ischemic heart disease. However, the lack of Q waves (NoQ) may be a readily available and specific marker for the presence of viability. The present study evaluates lack of Q waves on the ECG in the prediction of viability compared to dobutamine stress echocardiography(DSE) and rest-redistribution thallium-201(Tl-201)—imaging modalities that have shown high sensitivity and moderate specificity for predicting viability. Methods: Sixty four patients (age; 62짹9 yrs, male;51) with stable chronic coronary artery disease and ventricular dysfunction underwent rest ECG, DSE and Tl-201 scintigraphy before revascularization and a repeat rest 2D echo > 3 months later. Recovery of function was defined as occurring in ��� 2/16 ventricular segments. Findings: Compared to patients with Q waves (n= 48), those without Q waves (n=16) had a higher left ventricular ejection fraction (43짹14% vs. 33짹12%, p=0.017) and lower wall motion score index (1.69짹0.49 vs. 2.06짹0.46, p=0.009) at baseline. Total viability at baseline (% of total segments) was also higher in the NoQ group by Tl-201 scintigraphy (87짹19% vs. 70짹20%, p=0.008) and by DSE (81짹20% vs. 65짹24%, p=0.013). As expected, the sensitivity of NoQ waves was low in predicting recovery of function (23%) and inferior to Tl-201 (82%) and DSE (84%) (p<0.05). However, specificity of NoQ waves for predicting recovery of global function was high (72%) and higher than Tl-201 (50%) and DSE (45%). Results were similar if the data was analyzed regionally [Left anterior descending territory( LAD): specificity for NoQ= 81%, Tl-201= 44%; DSE = 51%; specificity for non-LAD territory: NoQ = 79%, Tl-201 = 55%, DSE = 53%). Conclusions : Lack of Q waves on the ECG is an important, readily available specific marker of myocardial viability in patients with suspected hibernation.