Left ventricular functions are among the most important predictors of prognosis in cases with coronary artery disease. Cases with moderate or high degree of left ventricular function are at high risk of death and correct evaluation of myocardial viability is clinically important while they are under medical therapy. In a considerably high percent of these patients, significant improvements occur in left ventricular functions after successful revascularization. In both left ventricular function and viability assessment there are many invasive and non-invasive (echocardiography, nuclear imaging, computerized tomography, magnetic resonance imaging, etc.) diagnostic methods. Here in this paper we will discuss solely role of echocardiography in the assessment of viability in patients with left ventricular dysfunction.