This book introduces molecular imaging and Target Therapy in various cancers. The first part is the subjects and primary focused on the basics of nuclear physics, radiation dosimetry, nuclear medicine equipment and small animal imaging equipment. The second part is about the radiopharmaceutical and commonly used clinical radiopharmaceuticals, including positron emission imaging agent, single photon emission imaging agent, and radionuclide therapy agents as well as their radioactive preparation, quality control, and a brief clinical application were included. Also, this part introduces a number of new imaging agents which were potential value of clinical applications. In the third part, the clinical application of the conventional imaging agent 18F-FDG in different tumors and neurodegenerative diseases and 18F-Dopa imaging in the nervous system are discussed. Besides the clinical applications of 99mTc labeled radiopharmaceuticals in parathyroid disease, coronary heart disease, myocardial infarction, sentinel lymph node, metastatic bone tumors, liver and gallbladder disease in children are introduced. Finally, the applications of radionuclide 131I on treatments of Graves' disease and differentiated thyroid cancer and metastases are investigated respectively. This book is a useful reference for professionals engaged in nuclear medicine and clinical research, including clinical nuclear medicine physicians, nuclear medicine engineers and nuclear medicine pharmacists.