Background Malnutrition at diagnosis is found in 10–50% of children with cancer in industrialized countries. In developing countries a large proportion of the normal paediatric population is undernourished and children with cancer often present late with advanced disease. Therefore it would be expected that many children with cancer are malnourished at admission. Malnutrition is associated with more severe chemotherapy toxicity and infectious complications. Methods All new paediatric oncology patients admitted in the Queen Elizabeth Central Hospital, Blantyre, Malawi between 1, January 2007 and 1, January 2008 were included. We documented age, clinical diagnosis, HIV status, weight, height, mid-upper-arm-circumference (MUAC) and triceps skinfold (TSF), and calculated arm muscle area (AMA). Nutritional data were compared with the 1978 NCHS growth curves. Results Of 128 children, 70 (55.1%) had an AMA for age