The purpose of this study was to determine the dental and skeletal effects of facemask therapy, and to evaluate the effect of age on treatment response. The material consisted of lateral cephalometric radiographs of 34 subjects with Class III malocclusions treated with a Delaire type facemask. Two groups of 17 patients each were formed: an early (six girls, 11 boys) and a late treatment group (eight girls, nine boys). At the beginning of treatment, the mean ages were 9 years 8 months for the early treatment group and 12 years 6 months for the late treatment group. The average treatment time was 7 months for both groups. A control group consisting of 17 children with a mean age of 9 years 5 months was formed that matched only the early treatment group according to age, and sagittal dental and skeletal relationships. To differentiate the orthodontic and total effects of the Delaire type facemask, superimpositions were made. In both treatment groups forward displacement of maxilla and an increase in overjet were found to be statistically significant (P < 0.01). Evaluation of total superimpositions showed that there was a significant displacement of maxillary molars and incisors (P < 0.05, early treatment group; P < 0.01, late treatment group), while no significant change was observed in local superimpositions. Changes in overjet and SNB in the early treatment group showed a significant difference compared with the control group (P < 0.001). The increase in Co-A and the decreases in the maxillo-mandibular differential and Wits' appraisal showed significant differences compared with the control group (P < 0.01). No significant difference was observed in skeletal and dental antero-posterior changes between the treatment groups.