Patients with severe ventricular dysfunction and coronary artery disease have high morbidity and mortality but may benefit from revascularization. However, there is also significant peri-operative morbidity and mortality among these patients. This accounts for the variable approach to these patients in different cardiac centres. Clearly this patient group has the most to gain when coronary revascularization is beneficial, but also the most to lose when it is not helpful. There is a need for an approach that can better define patients with severe ventricular dysfunction due to ischemia, who will be more likely to benefit from revascularization. Positron emission tomography (PET) imaging with F-18-Fluorodeoxyglucose (FDG) has been used to evaluate patients with ventricular dysfunction, to detect ischemic but viable myocardium more likely to recover from revascularization. Recently retrospective studies have shown that FDG PET can identify patients at high risk for cardiac events if they do not undergo revascularization. However, these studies did not evaluate whether FDG PET actually directed therapy decisions and because of their study design, could not determine whether FDG PET altered patient outcome. Our recent studies have shown that FDG PET can have important impact on therapy decisions and that patients with ischemic but viable myocardium are at increased risk. However it remains unclear whether an approach which utilizes FDG PET to define ischemic but viable myocardium can have a beneficial effect on patient outcome. It is also important to consider the potential clinical impact of FDG PET balanced against its limited availability. In addition, despite the cost of the technology, preliminary data from our group and others suggest a potential cost savings. Accordingly, a prospective randomized study is needed to evaluate whether FDG PET directed therapy has a beneficial effect on patient outcome and is cost-effective.