 Malnutrition and cachexia have a negative impact on the course of treatment in patients with head and neck squamous cell carcinoma (HNSCC). Good evidence exists for the practical use of the bioelectrical impedance analysis (BIA) parameter phase angle (PA) for the evaluation of nutritional and overall health status in cancer patients. In the present study, two hypotheses were tested: that PA can distinguish between malnutrition and cachexia; in non-cachectic patients, pre-treatment PA is predictive for cachexia development during (chemo)radiation.