Radiotheranostics is characterized by labeling high quality tumor-seeking compounds with imaging radionuclides for imaging and labeling with therapeutic radionuclides for therapeutic use. Although the nuclear medicine approach of fusing imaging and therapy is no doubt effective, the point is to recognize that it is not always necessary to carry out both imaging and therapy in a series, and how it is effective to carry out imaging and therapy respectively is the point. It may depend largely on the disease that is dealt with. In the therapy, it is of great concern to make optimum use of α emitters in addition to the conventional β emitters. In the future, theranostics technology and its application to personalized medicine will bring great benefits.