Myocardial viability testing can identify patients with ischaemic heart disease and left ventricular dysfunction who can potentially benefit from both improved cardiac function and prognosis after revascularisation. Evaluation of myocardial glucose metabolism by 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is considered the most sensitive tool to detect viability, and it predicts functional recovery as well as improved prognosis upon revascularisation. In parallel with the improved availability of PET, scanners have been changed into hybrid devices consisting of both multidetector computed tomography (CT) and PET (PET-CT). The immediate benefit for viability imaging is the ability to merge the coronary CT angiography images with FDG PET viability data. In addition, the possibility to utilise CT for myocardial viability imaging, such as delayed-enhancement imaging of myocardial infarction with acceptable radiation dose has been intensely investigated. This review will describe the principles of viability assessment by PET, and discuss the possibilities provided by hybrid PET-CT in this setting.