As in single photon emission computed tomography (SPECT), positron emission tomography (PET) involves the injection of a radiopharmaceutical, the physiological properties of which determine its distribution within the patient. The labelling radionuclide then allows this distribution to be imaged. The value of cardiac PET as a routine clinical tool, particularly for perfusion imaging, was previously limited by the expense and scarcity of cameras and the short half-lives of the radionuclides with complex radiochemistry. The need for an on-site cyclotron to produce these radiopharmaceuticals made a clinical service non-viable. A number of recent developments, however, have led to renewed interest in cardiac PET. This chapter covers PET instrumentation, detail on the radiopharmaceuticals used in cardiac PET, and a number of sections on F-fluorodeoxyglucose (F-FDG) PET covering infection and inflammation imaging.