A term “theranostics” is a compound word made with “therapeutics” and “diagnostics.” Discovery of X-ray has been made an extraordinary contribution in the medical science field. Development of computer science after World War II is absolutely imperative for the development of medical imaging technology to date. Invention of X-ray CT has been revolutionized medical image diagnostic systems. Several functional imaging modalities were emerged in not only radiological field but also magnetic resonance and ultrasonic fields. MR Redox imaging, EPR oxygen mapping, and hyperpolarized 13C MRI techniques in the magnetic resonance field has been able to fuse together on a digital imaging basis to achieve presumable theranostics. Future development of a suitable contrast agent for each imaging modality will be a key for success theranositics.