In oncogeriatric patients, severe malnutrition is associated with increased morbidity and mortality, nosocomial infections, radiotherapy or chemotherapy toxicities, and decreased of quality of life. Therefore, systematic screening and care of malnutrition is mandatory, in accordance with the French guidelines in 2007. Now, dietary counselling should be purposed systematically in malnourish patients and when radiotherapy or radiochemotherapy are considered. Oral supplementation by specific diet (immune-enhancing diets) should be used with cautions, and actually, reserved only in digestive neoplasms and surgery. In cases of severely malnourished patients or if dietary counselling suffers a setback, enteral nutrition should be recommended. In radiotherapy or chemotherapy, used parenteral nutrition is associated with an increase in infectious complications. Artificial nutrition should not be used when Karnofski index is lesser than 50% (or performance status greater than 2) and prognosis lesser at three months.