Nasal septum surgery is frequently performed to establish a functional nasal airway. In these patients obstructive sleep apnea syndrome (OSAS) is frequently present. Although patients with OSAS are at increased risk for hypoxemia, the impact of postoperative nasal packing (PNP) on sleep-disordered breathing and oxygen desaturations in patients with OSAS is unknown. We consecutively investigated 40 patients undergoing endonasal surgery receiving PNP. Fifteen of these patients had previously diagnosed OSAS (Group 2) and 25 did not (Group 1). In the control group, 12 healthy patients underwent elective ear or neck surgery without PNP. During the preoperative and postoperative nights, we continuously measured oronasal flow, thoracoabdominal movements, and oxygen saturation. We calculated the apnea-hypopnea index (AHI) and the oxygen-desaturation index (ODI). Compared with the preoperative values, after the operation, neither AHI nor ODI changed in the control group. In contrast, in Group 1, AHI (from 11 [5-19] to 37 [22-49]) and ODI (from 4 [2-8] to 13 [6-21]) significantly increased (P < 0.05), whereas in Group 2, only AHI significantly increased (from 14 [10-21] to 39 [26-50]); ODI remained similar (13 [8-27] versus 11 [4-37]). Because ODI did not increase in patients with OSAS and PNP who received postoperative oxygen overnight, postoperative intensive care monitoring might not be necessary on a routine basis for all patients with PNP and OSAS.