Objective: To examine the spontaneous leptin secretion in patients with myelomeningocele (MMC) and growth hormone deficiency (GHD). Methods: Serum leptin levels were studied in 10 prepubertal MMC patients with GHD (CA 6.2 ± 0.5 years), 10 patients with idiopathic GHD (IGHD; CA 7.6 ± 0.7 years) and 12 children with normal variant short stature (NVSS; CA 7.6 ± 0.5 years). Mean BMI (kg/m<sup>2</sup>) values of the groups did not differ significantly. Nocturnal leptin levels were analyzed over 10 h (blood samples every 20 min) and measured by specific radioimmunoassay. Results: Mean leptin concentrations did not correlate with BMI in MMC patients. Nocturnal leptin secretion of MMC patients was significantly different to those of children with IGHD and NVSS. Morning leptin levels did not decline as observed in both other groups. Conclusion: Since all groups were matched for BMI values, we suggest a hypothalamic dysregulation of leptin secretion in MMC patients.