Integration of multi-modal biomedical images of the heart (PET, SPET, MRI, Echocardiography) is a diagnostic procedure of increasing interest. Different registration techniques can be used to spatially correlate two independent tomographic scans of the same patient, each technique presenting relative merits and limitations. Integration of cardiac with respect to neurological images is difficult, because the heart is a non-rigid and moving organ. The experiences of this approach of integrated diagnosis are thus limited to date. However, registration of PET, SPET, MRI, Echocardiographic images has been described with accuracy considered acceptable for clinical applications. Registration techniques for the integration of multi-modal biomedical images of the heart, the clinical applications of cardiac image fusion and the experiences reported in the literature are presented in this paper.