Objective To investigate the functional polarization of T cells in children with obstructive sleep apnea hypopnea syndrome (OSAHS).Methods Forty five cases of OSAHS children were chosen to undergo tonsillectomy and adenoidectomy.Preoperative analyses of peripheral blood Th1 /Th2 ratio and Tc1 /Tc2 ratio were compared with those of normal children and those of postoperative 6 months for observation of the change of T cells.Th1/Th2 ratio and Tc1/Tc2 ratio were detected by flow cytometry.Results The preoperative ratio of Th1 cells in children with OSAHS was significantly lower than normal children [(9.66 ± 3.73) ％ vs (13.34 ± 4.36) ％,P ＜ 0.05],while the preoperative ratio of Th2 cells was significantly higher than normal children [(3.42 ± 1.64) ％ vs (2.53 ± 1.97) ％,P ＜ 0.05],which made the Thl/Th2 ratio lower than normal children (3.51 ± 1.53 vs 5.41 ±2.17,P ＜0.05).At the 6th month after tonsillectomy and adenoidectomy,the postoperative ratio of Th1 cells was significantly higher than preoperative ratio [(12.99 ± 3.68) ％ vs (9.66 ± 3.73) ％,P ＜ 0.05],while the postoperative ratio of Th2 cells was lower than preoperative ratio [(2.62 ± 1.88) ％ vs (3.42 ± 1.64) ％,P ＜ 0.05],which made the postoperative Th1 /Th2 ratio higher than preoperative ratio (5.15 ± 1.86 vs 3.51 ± 1.53,P ＜ 0.05).There was no significant difference in Tc1 /Tc2 ratio between the OSAHS children and normal children.Conclusions Functional polarization of T cells was abnormal in OSAHS children accompanied by the predomination of Th2 cells and the normal Tc cell polarization.Functional polarization of T cells can return to normal at the 6th month after tonsillectomy and adenoidectomy.