Molecular imaging is a new field by which molecular behavior and function in the living body can be visualized noninvasively. In view of the worldwide explosion of interest in this field, we have established the Molecular Imaging Center at the NIRS, which has long experience with medical imaging technologies including positron emission tomography(PET) and magnetic resonance imaging(MRI). The Center conducts an extensive range of studies, from basic science and technology for molecular imaging to application studies for diagnosis and pathophysiology of oncology and psychiatry. Current projects include the development of molecular probes and radiopharmaceutical production techniques and the investigation of measurement techniques for PET and MRI, in addition to preclinical and clinical applications in oncology and psychiatric and neurological diseases. The Center, as a world leader in molecular imaging research, provide facilities, equipment, and support systems for these studies.