Objectives:. Chronic upper airway obstruction may lead to right ventricle (RV) dysfunction by hypoxemic pulmonary vasoconstriction. Adenotonsillar hypertrophy (ATH) is the most common cause of upper airway obstruction in children. So we evaluate right ventricular function in children with severe ATH. Methods: Fifth children (aged 4~15 years, median 87 months, M:F =10:5) with severe ATH and forty healthy controls matched by age and sex were included in the study. Tricuspid annular plane systolic excursion (TASPE), RV myocardial performance index (RVMPI), and shortening fraction of RV outflow tract (RVOT-SF) were measured by transthoracic echocardiography. The level of serum pro-BNP was also analyzed. Result: Most children in the ATH group had highly positive in the Snoring-Tireness during daytime-Observed apnea-High blood pressure (STOP) questionnaire. The level of serum pro-BNP was significantly higher in the patient group in comparison with the control (54.47±34.40 vs 27.85±8.89; P=0.029). The Z-score of TASPE was lower (-0.20 ± 2.09 vs 0.32 ± 2.33; P=NS) and RVMPI was higher (0.42 ± 0.09 vs 0.36 ± 0.10; P=NS) in the ATH group, but not statistically significant. RVOT-SF had no differrence between the patient and control group. Conclusion: We couldn’t confrim the echocardiographic evidence of RV dysfunction in children suffering from upper airway obstruction. However, serum level of pro-BNP was significantly higher in the patient group. This finding suggests that chronic airway obstruction in children with severe ATH may have a risk for cardiac dysfunction. So we will have to investigate more patients with ATH by transthoracic echocardiography to confirm the association of the ATH and cardiac dysfunction. Pediatrician and otolaryngologist should consider cardiologic aspect during management of chidren with severe ATH.