The use of positron emission tomography (PET) in cardiology is growing rapidly. Technical features make PET a strong technology for the non-invasive evaluation of cardiac physiology. It is currently considered the most reliable tool for the identification of myocardial viability and also allows accurate assessment of myocardial perfusion and detection of coronary artery disease (CAD). The unique feature of PET is that myocardial perfusion can be measured in absolute terms, improving sensitivity in the detection of multivessel of disease and also allowing evaluation of very early changes in coronary vasoreactivity and the progression or regression of CAD. Use of the newest generation of PET systems with integrated multislice computed tomography (CT) is becoming a standard technique for cardiac imaging. Since the PET and CT techniques ideally complement each other the combination is particularly attractive for the non-invasive assessment of CAD but also has other functions. Finally, there are also promising future applications that involve molecular imaging of cardiac targets, which may further enhance the clinical utility of PET and hybrid imaging.