The purpose of this study was to compare the effects of rapid maxillary expansion (RME) and surgically assisted rapid maxillary expansion (SARME) on nasal volume using acoustic rhinometric methods. Two groups of subjects were used in the study. Group 1 consisted of 10 subjects (mean age 12.30 +/- 0.82 years) who were treated with RME, and group 2 consisted of 10 subjects (mean age 18.70 +/- 2.54 years) who were treated by SARME. In both groups, all cases had a maxillary width deficiency with bilateral crossbites. Nasal volume records were taken by the same otorhinolaryngologist with an AR device. AR recordings were performed for each patient with and without the use of a decongestant. The first record was taken before expansion, and the second record was taken at the end of retention. The data for both groups were evaluated using Wilcoxon signed rank test and Mann-Whitney U-test. The nasal volume showed a significant increase in both the RME and the SARME groups (P <.05). The measurement with the use of decongestant was similar to that without use of decongestant on the both groups (P <.05), but the different increments in nasal volume between the RME and the SARME groups were not statistically significant. Although the mean ages between the RME and the SARME groups were different, the increase in nasal volume was similar in both groups.