Imaging of the cardiovascular system with a combination of positron emission tomography (PET) and computer tomography (CT) or with a combination of single-photon emission computerized tomography (SPECT) and CT holds great promise for the future. Owing to the movement of the heart and the great vessels due to heart contraction and respiration this is, however, not straightforward. This article provides an overview over the principles of combined PET/CT or SPECT/CT imaging. It points out technical challenges inherent in imaging of cardiovascular system and presents possible solutions that allow for optimal fusion and motion correction of the combined molecular, functional and morphological image data.