OBJECTIVES/HYPOTHESIS: The primary objective was to evaluate the association of palatine (T/P) tonsil size determined by radiography with pulmonary artery pressure (PAP) measured by Doppler echocardiography in children with surgical indication for adenotonsillar hypertrophy. The secondary objective was to evaluate if tonsil size could help to identify children at higher risk of pulmonary artery hypertension (PAH). STUDY DESIGN: Cross-sectional study. METHODS: The study was conducted with a consecutive sample of children with indication of adenotonsillectomy for sleep-disordered breathing. T/P was measured by lateral neck radiography, PAP by echodopplercardiography, and symptoms and quality of life by the Obstructive Sleep Apnea (OSA)-18 questionnaire. T/P was plotted in a receiver operating characteristic (ROC) curve to determine the best cut-off point to identify children with PAH. RESULTS: A total of 45 children participated in the study. The mean age was 72.0 +/- 32.3 months, and six (13%) patients had PAH. Correlation between systolic PAP and T/P was strong (r = 0.624; P < .0001). T/P was significantly higher in patients with PAH (P < .001). OSA-18 score did not significantly correlate with the variables. The cut-off point identified in the ROC was 0.66, which was the minimum T/P where sensitivity was still 100%. Mean systolic pulmonary artery pressure in children with T/P >0.66 was significantly higher than in those with T/P <0.66 (P < .001). CONCLUSIONS: T/P showed a good correlation with PAP in children with adenotonsillar hypertrophy and surgical indication for sleep-disordered breathing. Children with T/P >0.66 can be at greater risk for cardiac complications and should be submitted to complementary studies with echodopplercardiography or given preference for surgery.