Complementary information provided by Single Photon and Positron Emission Tomography (SPECT and PET) in nuclear cardiology allows a better comprehension of the physiopathology of the heart. In this work a surface matching registration technique is evaluated in the spatial correlation of SPECT and PET cardiac images. The method is based on matching correspondent anatomical surfaces extracted from transmission (TR) SPECT and PET studies, usually performed for attenuation correction. The accuracy of the technique was evaluated by phantom experiments and on patient data ( 2 0 1 Tl SPECT and 1 3 NH 3 PET perfusion studies). An application of the method is presented for the correlation of SPECT 2 0 1 Tl perfusion and PET 1 8 FDG metabolic studies in the evaluation of myocardial viability.