High-resolution three-headed single photon emission computed tomography (SPET) equipped with fan-beam collimators was applied to myocardial perfusion imaging in infants aged from 1 to 11 months (n = 5). A tabletop designed specifically for infants was fixed on the SPET couch to reduce the radius of camera rotation to 13.2 cm. Significant improvement in resolution was achieved with the fan-beam collimators compared to parallel-hole high-resolution collimators. With the administration of approximately 37 MBq (26-44 MBq) 201Tl, 5 min acquisition time was possible for SPET imaging, which provided good image quality in all patients. Thus, a smaller administration dose is possible within a practical short acquisition time. High-resolution fan-beam SPET imaging can be a routine diagnostic method for heart disease in newborn babies and infants.