Objective: To investigate the duration criterion of respiratory events in children with obstructive sleep apnea syndrome (OSAS) by analyzing standard nocturnal polysomnograms (PSG). To provide reference values for pediatric PSG. Methods: 107 OSAS children diagnosed by PSG from January 2004 to May 2006 were randomly selected. The decrease in arterial oxygen saturation (Delta SaO(2)) and the corresponding event duration of each respiratory event were observed. Results: (1) There was significant positive correlation between oxygen desaturation values (Delta SaO(2) = 0-17%) and the corresponding durations of respiratory events (P < 0.001). (2) There was no significant difference in durations of respiratory events in rapid eye movement (REM) sleep and NREM sleep, the demographics between male and female children. (3) Significant positive correlation between age and duration of respiratory events (apnea/hypopnea) when oxygen desaturation values equal to 4% (Delta SaO(2) = 4%) was observed. (4) The lower limit of 95% confidence intervals of which duration of oxygen desaturation value equals to 4% was 5.4 s. Conclusion: (1) PSG studies may allow the establishment of the duration criterion of significant respiratory events; (2) 5.4 s can be defined as duration criteria of respiratory events; (3) the present study provides reference values for Pediatric PSG. (C) 2015 Elsevier Ireland Ltd. All rights reserved.