Positron emission computed tomography (PET) provides high quality tomographic images of the heart with accurate attenuation correction. The use of various compounds labeled with ultra-short lived positron-emitting radionuclides, such as 11C, 13N, 15O and 18F, allows physiological and biochemical measurements in vivo. Recently, a few institutions in Japan have introduced this technique into cardiology. Although it requires an enormous cost both for the equipment and for running the system, it is expected to play a major role in nuclear cardiology in the near future.