Pervasive developmental disorder (PDD) and attention deficit hyperactivity disorder (ADHD) are likely to be associated with increased oxidative stress, particularly that of lipid peroxidation. We evaluated the oxidative stress status of pediatric PDD and ADHD patients using their urine samples. Urinary acrolein-lysine levels in 11 PDD and 10 ADHD children (205 ± 97 and 234 ± 75 nmol/mg Cr, respectively) appeared higher than those of the control subjects (155 ± 59 nmol/mg Cr). Measurement of urinary specific biomarkers is comfortable, non-invasive, and easy to perform in children. Our findings might provide a scientific guide for use in further clinical and biochemical studies of these disorders.