Cancer is the second leading cause of death in the world. Radiolabeled nanocarriers or nanoparticles can be designed and used for cancer diagnostic and therapeutic purposes when tagged with appropriate radionuclides. Current progress in nanotechnology and nanomedicine has exploited the possibility of designing tumor-targeted nanocarriers able to deliver radionuclide payloads in a selective manner to improve the efficacy and safety of cancer imaging and therapy. The major nanocarriers include liposomes, dendrimers, quantum dots, iron oxide and carbon nanotubes. In addition, the combining of tumor specific multifunctional and multimodality nanocarriers will hopefully achieve earlier tumor detection and better tumor treatment. Several radiolabeled multifunctional and multimodality nanoparticles have been effectively demonstrated in detecting and treating cancer in animal models. However, further preclinical and clinical efficacy and toxicity studies are required to translate these advanced technologies to the health care of cancer patients. The aim of this article is to provide a brief overview of current status of applications, advantages and up-to-date research and development of nanotargeted radiopharmaceuticals in cancer imaging and therapy.