Objective : The purpose of this longitudinal retrospective study was to evaluate transverse maxillary expansion after a Schuchardt or segmental posterior subapical maxillary osteotomy (SPSMO) in patients with cleft lip and palate (CLP). A second aim was to compare these data with data for adult patients without CLP who were receiving a surgical assisted rapid palatal expansion (SARPE). Method : The study group comprised 19 patients with CLP and a severe transversally collapsed maxilla who were treated with SPSMO followed by hyrax expansion at the University Hospitals Leuven. Dental casts of the 19 patients were analyzed before treatment, at maximum expansion, during orthodontic treatment, at the completion of orthodontic treatment. and 2 years after orthodontic treatment and were measured at the canine, premolar, and molar levels. Adult patients without CLP who were enrolled in a prospective study served as the control group. Results : Maxillary expansion within the study group was significantly greater (P < .05) at all measured levels compared with the maxillary arch before treatment. No significant relapse was measured in the study group 2 years after orthodontic treatment. When comparing the study and control groups, the only statistical difference was that canine expansion was significantly greater in the study group. Conclusion : SPSMO followed by maxillary expansion and orthodontic treatment is an appropriate treatment option to correct a severe transversally collapsed maxilla in patients with CLP. The overall treatment effect of SPSMO expansion is comparable with the effects of SARPE, although canine expansion was greater in the SPSMO group.