The concept of multimodality imaging has been developing rapidly in recent years due to the need to integrate information on anatomy (which defines coronary artery disease) with functional data (which reflects the effects of this disease on tissues) to enable the proper evaluation of patients with ischemic heart disease. From the clinical point of view, it has been well established that a complete evaluation of a coronary lesion requires not only morphological information on the location of the stenosis, but also functional information on its impact. Van Werkhoven et al have demonstrated that the combination of anatomical and functional information can improve patient risk stratification. Thus, patients with 50% coronary occlusion associated with perfusion defects experienced a higher annual event rate during follow-up (9%) than patients with no significant coronary lesions or perfusion defects (1%). While the severity of ischemia is related to the degree of stenosis, this relationship is not always linear. A number of factors apart from the degree of occlusion (assessed by coronary luminography) establish whether or not a given stenosis induces a myocardial perfusion defect. Among these factors, we stress the importance of the existence of collateral circulation and the phenomenon of arterial vasospasm, a functional mechanism that can overlap a mild fixed lesion, leading to significant occlusion. In addition, a nonsignificant arteriosclerotic plaque can become destabilized and produce serious or even total arterial occlusion. Moreover, the phenomenon of ‘‘ischemic preconditioning’’ could play a role in the discrepancy between anatomical and functional changes. Given all these circumstances, evaluation of the functional relevance of the coronary stenosis is recommended to guide revascularization strategies. If, in addition, this dual information can be obtained using noninvasive methods and can be presented jointly (by means of image fusion), the result facilitates optimal clinical decision-making, while also reducing the risk inherent in invasive diagnostic techniques. Since the 1990s, stress and rest myocardial perfusion scintigraphy has been developed as an excellent noninvasive method to obtain the functional information required for the assessment of