Book excerpt: Molecular imaging of drugs or drug carriers is a valuable tool that can provide important information on spatiotemporal distribution of drugs, allowing improved drug distribution at target sites. Chemically labelled drugs can be used to both diagnose and treat diseases. This book introduces the topic of image guided drug delivery and covers the latest imaging techniques and developments in theranostics, highlighting the interdisciplinary nature of this field as well as its translational ability. These technologies and techniques hold potential for individualised, safer therapies. The book introduces the chemistry behind labelling drugs or drug carriers for imaging. It then discusses current scientific progress in the discovery and development of theranostic agents as well as the latest advances in triggered drug delivery. Novel imaging techniques that can be combined with therapeutics are presented, as well as results and findings from early clinical trials. This text will provide postgraduates and researchers in various disciplines associated with drug discovery, including chemistry, device engineering, oncology, neurology, cardiology, imaging, and nanoscience, an overview of this important field where several disciplines have been combined to improve treatments. Readers will be introduced to techniques that can be translated to the clinic and be applied widely.