The aim of this study was to determine the cephalometric changes in subjects with Class III malocclusions after rapid palatal expansion (RPE) and facemask treatment. The 30 subjects presented with developing Class III malocclusions. The treatment group comprised 15 patients (eight girls and seven boys, mean age 11 years 6 months) who had undergone RPE and facemask therapy. The control group consisted of nine girls and six boys with a mean age of 11 years 8 months. Radiographs were take at the same time intervals for both groups, and the average treatment time was 15 months. A Wilcoxon test was used to determine significant differences before and after treatment, and a Mann-Whitney U-test to analyse differences between the treatment and control groups. In the sagittal plane, significant changes were observed in both groups. In the treatment group, the following dimensions increased significantly: A perpendicular to FHp (P < 0.001), ANS-PNS (P < 0.01), 6 perpendicular to FHp (P < 0.05); in the control group Go-Gn (P < 0.05) increased significantly. In the treatment group, SN/Go-Gn and SN/ANS-PNS had higher values and this finding was significant (P < 0.05). Managing developing Class III malocclusions with RPE and maxillary protraction presents favourable results, such as vertical and sagittal displacement of point A.