Introduction: In this study we analyzed dentoskeletal effects of orthopedic therapy with rapid palatal expander (RME), used according to modified Alt-RAMEC protocol, followed by facial mask in preadolescent patients with class III malocclusion. Materials and methods: The sample consisted of 10 patients treated consecutively with the alternate rapid maxillary expansions and constrictions (Alt-RAMEC) protocol and facial mask before the pubertal growth spur the patients were re-evaluated after about one year of treatment. We compared the cephalometric analyses at T0 (before the treatment) and T1 (just after the end of the treatment—about 1 year), evaluating 18 parameters. The normality of each distribution was assessed with D'Agostino-Pearson normality test and significative differences between T0 and T1 were assessed with paired t test (p < 0.05). Results: Sagittal measurements of the maxilla (SNpSNa distance) showed significant improvements (p < 0.0001) with protraction effect at point A. Significant improvements were recorded also at Wits appraisal and overjet. Measures of the mandibular growth (Co-Gn) showed increased values at T1, as well as vertical dimension (SNpSNa-GoGn). No significant variations were recorded at the dental parameters. Conclusion: This protocol induces important skeletal effects, like advancement of the maxilla, also in preadolescent patients, while dental changes are minimal. Alt-RAMEC protocol seem to modulate maxillary development in patients near the pubertal growth spurt.