Objective: To evaluate the effects of combined rapid maxillary expansion (RME) and face mask (FM) therapy during the mixed dentition period on the dental arch length in patients with skeletal Class III malocclusion. Study Design: We evaluated pre- and post-treatment orthodontic models of 52 patients (25 girls, 27 boys) aged 8-12 years with skeletal Class III malocclusion(ANB<0) accompanied by maxillary transverse deficiency and retrognatism treated by bonded RME-FM therapy for a mean duration of 8 months. Palatal rugae, the cusp tips of permanent first molars, deciduous molars/permanent premolars, deciduous canines and the incisal edges of permanent central incisors were marked on orthodontic models, which were then photocopied. Inter-molar, inter-premolar and inter-canine widths; the arch length; the arch depth and molar and incisor sagittal movements were measured on these photocopies. Statistical comparisons were made using paired t-tests. Results: Inter-molar, inter-premolar and inter-canine widths and the arch length showed significant increases after treatment, while the arch depth showed a significant decrease (p<0.001 for all). Conclusions: With the study limitations, our results suggest that combined RME-FM therapy increases the arch length in the mixed dentition of patients with skeletal Class III malocclusion.