Introduction: The aim of this study was to compare the dentoalveolar treatment effects of 3 rapid maxillary expansion (RME) appliances, supported by different tissues, on the maxilla and the mandible. Methods: Patients were assessed for eligibility, and those who met the requirements and agreed to participate were enrolled in the study. Participants were randomly allocated into 3 groups, depending on the type of expansion. The tooth-borne group (n = 16; ages, 12.63 +/- 1.36 years) had RME with a tooth-borne appliance; the bone-borne group (n = 16; ages, 12.92 +/- 1.07 years) had RME with a bone-borne appliance; and the hybrid group (n = 15; ages, 13.41 +/- 0.88 years) had RME with hybrid appliances. Dentoalveolar effects were evaluated by digitally superimposed 3-dimensional scans of maxillary dental casts on a coordinate system and linear interdental width measurements of mandibular dental casts in the pretreatment, posttreatment, and postretention periods. For intragroup and intergroup comparisons, 1-way analysis of variance for repeated measures and multivariate analysis of variance were performed, respectively. Results: Similar dentoalveolar treatment effects were achieved in all groups with the exception of a small amount of expansion on the right side in the bone-borne group. Conclusions: All 3 expanders led to the expansion of maxillary dentoalveolar structures with mild relapse. However, the amount of expansion of the bone-borne expander on the right side was statistically lower. Spontaneous interdental expansion was observed in the mandibular dentitions in all groups.