Nuclear medicine is a wide field that, since its birth, is constantly characterized by technological evolution. The introduction of hybrid imaging systems was a breakthrough, allowing for higher diagnostic accuracy and spreading therefore the clinical applications of this modality. Nowadays, functional and anatomical information are essential for the current management of the patients, and modalities able to fuse and retrieve both these data have a significant role by providing comprehensive information on the state of the patient. Hybrid devices have now an increasingly important value in different clinical applications of nuclear medicine, in both positron emission tomography (PET) and single photon emission computed tomography (SPECT) systems. Insights on future perspectives are currently addressing the implementation of these technologies in the field of artificial intelligence and theranostics approaches.