ObjectiveThe effect of the modified step Le Fort I osteotomy on the inferior nasal structures and the nostril area was evaluated.Materials and methodsThis study included 24 patients who had modified step Le Fort I osteotomy. Inferior nasal concha volume (INCV), meatus nasi inferior volume (MNIV), the sum of both structures volume (TV), and nostril area (NA) were evaluated in pre- (T0) and postoperative (T1) periods.ResultsFor all patients, NA increased both on the right side (p = 0.011) and left side (p = 0.050) after surgery. The INCV and TV values were lower in T1 than those in T0; however, a statistically significant decrease of INCV and TV was found only in the right side of males (p = 0.039 and p = 0.050, respectively). No significant difference was found in MNIV between T0 and T1 measurements (p > 0.05).ConclusionMaxillary advancement with the modified step Le Fort I osteotomy technique increased the NA, which may have a positive effect on breathing function. On the other hand, although TV tended to decrease, MNIV did not change after surgery as the same decreasing tendency also existed in INCV.