OBJECTIVE: Aim of this study was to detect the changes in nasal volume due to bone-borne, surgically-assisted rapid palatal expansion (RPE) with the Dresden Distractor using computed tomography (CT). MATERIALS AND METHODS: 17 patients (mean age 28.8) underwent axial CT scanning before and 6 months after RPE. The nasal bone width was examined in the coronal plane. Cross-sectional images of the nasal cavity were taken of the area surrounding the piriform aperture, choanae and in between. Bony nasal volume was computed by connecting the three cross-sectional areas. RESULTS: All but two patients showed a 4.8% increase in nasal volume (SD 4.6%). The highest value, 33.3% (SD 45.1%), was measured anteriorly at the level of the nasal floor. This correlated with the midpalatal suture's V-shaped opening. There was no significant correlation between an increase in nasal volume and transverse dental arch expansion. CONCLUSION: As most of the air we breathe passes the lower nasal floor, an improvement in nasal breathing is likely.