Heart failure presents a significant problem in industrialized countries, with a high prevalence, morbidity, and mortality, where it is most frequently caused by coronary artery disease. Revascularization in patients with symptomatic heart failure has been associated with improved cardiovascular outcomes. Predictors of outcome benefit from revascularization include the presence and extent of hibernating myocardium, ischemia, scar, left ventricular ejection fraction, and renal function. Viability is useful in directing the management of patients with ischemic cardiomyopathy. It is especially useful in those with the highest risk where revascularization decisions are the most difficult. In the absence of definitive prospective randomized data on the benefit of routine viability testing in the management of ischemic cardiomyopathy, physicians will likely continue to use viability testing to assist them with their decision-making process. This review article focuses on the value of viability imaging and the modalities of its measurement, which include PET, SPECT, cardiac MRI, and dobutamine echocardiography. These imaging modalities should be seen as complementary rather than competing methods. In any given clinical setting, the indications, comorbidities, availability, local expertise, sensitivity, specificity, and limitations of each modality need to be considered. When advanced imaging (PET and cardiac MRI) are available, they are generally considered the preferred choice because of their overall higher accuracy. Finally, we explore the role of ischemia in patients with viability and the potential role of neurohormonal and viability imaging in deciding the need for implantable cardiac defibrillator as a primary prevention in patients with severe ischemic cardiomyopathy.