Copper radionuclides are rapidly emerging as potential diagnostic and therapeutic tools in oncology, particularly 64Cu-radiopharmaceuticals for targeting neuroendocrine, prostate, and hypoxic tumors. Unexpectedly, experimental results are also revealing the impressive biological behavior of simple [64Cu2+] ions. For example, it has been demonstrated that administration of ionic [64Cu2+] in physiological solution allows the selective targeting of a variety of malignancies. These remarkable biological properties appear to be crucially linked to the natural role of copper ions in cell proliferation. Here, we review the current status of 64Cu-radiopharmaceuticals in molecular imaging and cancer therapy.