We evaluated the role of adenotonsillar hypertrophy and facial morphology in children with obstructive sleep apnea (OSA) and compared these data with an age-matched control group. We performed cephalometric analysis to evaluate facial morphology using lateral facilal roentgenograms. Adenotonsillar and maxillary hypertrophy was remarkable in OSA children. Maxillary protrusion was significantly smaller in the OSA group than in the control group in older children (5-9 years old). Mandibular protrusion was significantly smaller in the OSA group even at younger ages (1-2 years old). The hyoid bone was significantly lower in the OSA group than in the control group at age 3-6 years. Both environmental factors due to upper airway obstruction and genetic factors are suspected as causes of abnormal facial morphology in OSA children.