Patients with obstructive sleep apnea (OSA) show high nasal resistance (NR). The present study tested the hypothesis that nasal obstruction in OSA patients could be caused by pharyngeal narrow. The aim of this study was to investigate the effect of uvulopalatopharyngoplasty (UPPP) on NR in patients with OSA. Rhinomanometry was performed and the Mallampati score was recorded during wakefulness in a sitting position before and after UPPP for 33 patients with OSA. Thirty-three healthy volunteers were used as a control group. The NR in patients with OSA (0.37 ± 0.22 Pa/cm(3)/s) was significantly higher than that of the normal controls (0.19 ± 0.04 Pa/cm(3)/s) (p < 0.01). The NR decreased from 0.37 ± 0.22 to 0.20 ± 0.05 Pa/cm(3)/s (p < 0.01) after UPPP with the Mallampati score decreased from 3.00 ± 0.56 to 1.52 ± 0.57 (p < 0.01). However, NR values after UPPP were still higher than those of the control group, but there was no significant difference between those two groups (p = 0.34). The present study showed that the high NR may not be completely attributable to nasal anatomic obstruction, but may result from pharyngeal narrow in OSA. High NR may be a result of OSA rather than a cause.