Gastrostomy tube (GT) feeding in children with cerebral palsy (CP) is associated with significant increases in weight gain and, potentially, with overfeeding. This study aimed to measure energy balance and body composition in children with CP who were fed either orally or by GT. Forty children (27 males, 13 females; median age 8y 6mo; range 1y 4mo-18y 11mo) with spastic quadriplegic CP, of whom 22 were gastrostomy-fed and 18 orally-fed, underwent anthropometry, indirect calorimetry, and total energy expenditure determination (doubly-labelled water method). Total body water content (estimated by the 18O dilution method) was used to determine body composition. The Gross Motor Function Classification System (GMFCS) was used to determine the degree of motor impairment. GMFCS levels ranged from I to V; in the gastrostomy group 19 out of 22 were Level V and two out of 22 were Level IV. Within the orally-fed group, 11 out of 18 were Level V and four out of 18 were Level IV. Resting metabolic rate and total energy expenditure of the gastrostomy-fed children were lower but they had a significantly larger triceps skinfold thickness (p=0.01) and fat mass index (p=0.02) than the orally-fed children. Both groups had consistently higher body-fat content and lower fat-free (i.e. muscle and bone) content than the reference population of age- and sex-matched children without disabilities. This study has demonstrated the relatively low energy expenditure and high body-fat content of children with severe CP and highlighted the potential risk of overfeeding with available enteral feeds administered via GT.