It has been proposed that the neurotrophin brain-derived neurotrophic factor (BDNF) may be involved in attention deficit-hyperactivity disorder (ADHD) etiopathogenesis. Alterations in BDNF serum levels have been observed in childhood/adulthood neurodevelopmental pathologies, but no evidence is available for BDNF serum concentrations in ADHD. The study includes 45 drug-naïve ADHD children and 45 age-sex matched healthy subjects. Concentration of serum BDNF was determined by the ELISA method. BDNF serum levels in patients with ADHD were not different from those of controls (mean ± SD; ADHD: 39.33 ± 10.41 ng/ml; controls: 38.82 ± 8.29 ng/ml, t = -0.26, p = 0.80). Our findings indicate no alteration of serum BDNF levels in untreated patients with ADHD. A further stratification for cognitive, neuropsychological and psychopathological assessment in a larger sample could be useful to clarify the role of BDNF in the endophenotype characterization of ADHD.