This book will facilitate the understanding of cross-sectional anatomy details and assist radiation oncologists in the difficult task of a detailed delineation of lymph node targets in multiple anatomical locations. It opens with a brief overview of the anatomy of the lymphatic system, followed by the main anatomical classifications involving the lymph drain in four main regions (head and neck, mediastinum, superior abdomen, pelvis) and describes the spreading patterns of the different cancers. Based on the close collaboration between radiologists and radiation oncologists, explicit instructions for the delineation of lymph nodal clinical target volumes are proposed to obtain a more accurate and consistent definition of these volumes of interest. In addition, axial topographic reference points for anatomical boundaries of regional lymph nodes are presented in illustrative tables. This book will be a valuable aid in accurate image-based radiation therapy planning for young as well as for more experienced radiation oncologists.