In recent years, there has been growing interest in developing therapeutic radiopharmaceuticals for treating various malignancies that express specific receptors on cancer cells. The concept of “Theragnostics” involves combining therapy and diagnostics by using radiopharmaceuticals that target the same receptors on cancer cells. The diagnostic agent, usually a gamma or positron emitter, is used for imaging, while the therapeutic agent emits beta or alpha radiation that binds to the tumor and destroys it. Because the binding is specific to the target receptors, tissue destruction occurs mainly in cancerous lesions, resulting in fewer side effects compared to external radiation or chemotherapy. The Theragnostics principle is illustrated in Figure 1.