BACKGROUND Nutritional status assessment and support should be considered a valuable measure within the overall oncology strategy. Despite extensive research in the field of clinical nutrition, definite guidelines to base rational nutritional assessment and support in cancer patients are still debated. This review examines different approaches to nutritional status in cancer patients. METHODS The assessment of nutritional status is usually based on anthropometric measures, biochemical or laboratory tests, clinical indicators and dietary assessment. At present, body composition (BC) is rarely measured in the clinical setting because it is thought to be too unmanageable and time-consuming. However, using new technologies, the estimation of fat, lean and body fluids, that is significant in the management of nutrition therapies in oncology, has become easy. The present study evaluates the different methods of nutrition assessment today available, especially body composition (BC) measurements. Furthermore, nutrition assessment, relevance of nutritional support and choice of nutritional strategy, in surgical patients, are discussed. CONCLUSIONS Given the clinical relevance of nutritional intervention in patients' quality of life, the nutritional status assessment has a key role in oncological and surgical practice and should include BC assessment in order to tailor nutritional treatment to patients' individual requirements. Furthermore, administration of the supplemented diet before and after surgery seemed to be the best strategy to reduce complications and length of hospital stay.