Summary The objective of this study was to examine maxillary skeletal stability after simultaneous modified LeFort III/LeFort I osteotomy in patients who presented for the simultaneous correction of midface and maxillary hypoplasia. Eleven patients underwent simultaneous modified LeFort III/LeFort I osteotomies using transoral and transconjunctival surgical approaches. The mean net surgical movement at A point (A pt) was 5.2 mm anteriorly and 2 mm inferiorly. Titanium mini-plates were used to stabilize both the midface component and the LeFort I segment; iliac crest or calvarial bone grafts as well as freeze-dried cancellous blocks were used at the zygoma and lateral orbital rim regions. All patients had lateral cephalometric radiographs taken immediately postoperatively, and at their sixth week, sixth month, and one year follow-up visits. Five maxillary landmarks (CI, A pt, ANS, PNS, and 2M) were used to examine the horizontal and vertical changes occurring at each time period. The central incisor relapsed vertically 2.8 mm at six months, A pt relapsed vertically 2.3 mm at six months, ANS relapsed posteriorly 1.6 mm at 6 weeks, PNS relapsed 1.5 mm anteriorly at one year. This study demonstrated that the maxilla moved anteriorly 1.5 mm and superiorly 2.8 mm in simultaneous modified LeFort III/LeFort I osteotomies performed with mini-plate fixation and bone grafts. This movement should be considered when planning and performing simultaneous surgical movement of the maxilla and midface using modified LeFort II/LeFort I osteotomies. Appropriate occlusal overcorrection at the time of surgery is necessary.