The planning of radiotherapy has known major developments during the last years. With the emergence of news techniques such as conformational radiotherapy, intensity modulated radiation therapy or stereotactic radiation therapy, the definition of target volumes was of great importance. The recommendations for the target volumes definition have been defined in the ICRU 50 and 62 reports, without any guidelines for volume delineation. Among the uncertainties that may influence the outcome after irradiation, the intra- and interobservers variations in delineation are the most important. Many teams have offered guidelines or atlases to homogenize these volumes and reduce these variations related to medical intervention. The aim of this paper is to present the main recommendations.