Aim: To investigate the prevalence of malnutrition, patterns of change in nutritional status (NS) and potential factors which may contribute to the development of malnutrition in newly diagnosed Scottish paediatric cancer patients. Methods: NS was assessed between Aug 2010-Oct 2013 using anthropometry, body composition and dietary assessment. The primary outcome was malnutrition defined as body mass index (BMI) according to UK guidelines. Frisancho's (1981) reference was used for arm anthropometry and to estimate muscle (FFM) and fat mass (FM). Correlations and multilevel analysis were performed. Results: 74 (78%) patients were recruited. At baseline, the prevalence of undernutrition was 9.5%, overnutrition 5% and obesity 11%. Triceps skinfold identified the highest prevalence of undernutrition 13.5% and the lowest of obesity 1%. BMI [p=0.03; 95% CI (-17 to-12)] and FM [p<0.05; 95% CI (677-1122)] significantly increased after 3 months and remained steady thereafter, whilst FFM [p<0.001; 95% CI (2992-3550)] significantly decreased during the first year. Only energy intake showed minor correlation with BMI (r=0.1; p=0.04) and TSF (r=0.2; p=0.03) at baseline. Conclusion: Undernutrition was more prevalent at diagnosis, yet overnutrition increased significantly during treatment. The changes seen in body composition emphasise the need to implement new strategies to improve the NS of paediatric cancer patients. :