Cancer is often associated with malnutrition and weight loss. The occurence of malnutrition during the course of the disease depends on the type, extent, and therapy of the tumor. Pancreatic cancer patients and patients with hepatocellular carcinoma are particularly at risk of developing a pronounced weight loss. Cancer-related malnutrition has negative impact on the response to therapy, survival, quality of life, and the infection rate of patients, resulting in prolonged hospital stays and higher costs for health care. Maintaining or optimizing the quality of life in patients receiving palliative therapy has priority. Since a poor nutritional status affects the quality of life, patients might benefit from the use of an adjusted amount of oral nutritional supplements.