This book provides an updated account of recent advancements in the field of nanotechnology-based theranostics with special emphasis on their application in the diagnosis and treatment of various types of cancer and neurological diseases. The book is divided into two sections; the first section provides an introduction to the nanoscale theranostics & radiopharmaceuticals. The second section highlights the importance of nanoscale theranostics in disease diagnosis & treatment. It presents the potential of nanotechnology for developing nanomedicine and nanotheranostics for the diagnosis and treatment of a variety of illnesses.  Further, the book discusses the usefulness of theranostic nanoparticles in the diagnosis of disease, identification of location, and stage, and in providing information about the therapy response. In addition, the book focuses on the clinical applications of nanomaterial radiolabeling in nuclear imaging of cancer and other illness. Towards the end, the bookexamines the toxicity, regulatory protocols, and future aspects of clinical applications of theranostics. This book is an invaluable source for academicians and industrial scientists working in multiple healthcare fields like pharmaceutical and biological sciences, life sciences, biotechnology, biomedical engineering, and nanobiotechnology.