Obstructive sleep apnea syndrome (OSAS) is a relatively frequent condition which may affect up to 2-3 percent of school age children. The morbidity of untreated OSAS may include failure to thrive, pulmonary and systemic hypertension, and behavioral and neurocognitive deficiencies. However, it remains unclear to what extent OSAS impinges on aspects of neurocognitive and behavioral function, and whether sleep fragmentation, intermittent hypoxemia, and alveolar hypoventilation, which are the three major physiological alterations in OSAS, selectively affect particularly vulnerable components of neurocognitive function. Furthermore, certain similarities exist between the behavioral alterations occurring in OSAS and those seen in children with the Attention Deficit Hyperactivity Disorder (ADHD).