Objective: This study aims to investigate the impact of upper airway obstruction (UAO) in children by measuring thoracoabdominal asynchrony (TAA) during periods of sleep apnea/hypopnea and during scored-event-free (SEF) breathing periods. Methods: Respiratory inductive plethysmographic signals were extracted from polysomnographic data, recorded before and after adenotonsillectomy in 40 children with UAO and 40 healthy, matched children at equivalent time points. Thoracoabdominal asynchrony was computed using a Hilbert transform-based phase difference estimation method in SEF periods during stage 2, stage 4 non-rapid eye movement (NREM), and rapid eye movement (REM) sleep and compared between the groups. Results: At baseline, in the UAO group, TAA during obstructions were significantly higher than TAA during SEF periods in both stage 2 and REM sleep. Compared to controls, children with UAO had a significantly higher TAA during SEF periods in stage 2, stage 4 sleep, and REM sleep. This between-group difference was not significant post adenotonsillectomy. UAO group showed a significant decrease in TAA compared to their baseline during SEF stage 2 and 4 NREM, but not in REM. Conclusion: Upper airway obstruction in children is associated with increased TAA during SEF periods, indicative of continuous partial obstruction of the upper airway. Adenotonsillectomy decreased this effect significantly in non-REM sleep as evidenced by reduced asynchrony levels post-surgery. TAA assessment during sleep may therefore provide additional diagnostic information.