There is a tendency to adiposity in patients with congenital adrenal hyperplasia (CAH) despite physiological corticosteroid doses. This study investigated body fatness in children with CAH under corticosteroid replacement therapy. Seventeen children with CAH (female:male, 9:8; age range 1.6-10.5 years) and 18 controls (female:male, 9:9; age range 1.4-10.2 years) were studied. Serum lipids, leptin, insulin, anthropometry, body circumferences, skinfold thickness, and body fat ratio as measured with bioelectrical impedance analysis (BIA) were the study parameters. Weight standard deviation scores (SDS), body mass index (BMI), BMI-SDS, body circumferences, skinfold thickness, and body fat ratio were higher and leptin was positively correlated with all of the body circumference and skinfold thickness parameters as well as body fat ratio in the study group. Waist/hip ratio was lower in the study group. Body fatness is a serious problem starting in early childhood in CAH patients and further refinement of the glucocorticoid replacement regimens as well as lifestyle measures are needed.