OBJECTIVE(S):Obstructive sleep apnea syndrome (OSAS) is a respiratory disorder which affects from 1 to 3 % of people during development. OSAS treatment may be pharmacological, surgical or based on application of intraoral devices to increase nasal respiratory spaces. The purpose of this study was to determine the efficacy of the Rapid Maxillary Expander in OSAS young patients by measuring cardio-respiratory monitoring parameters (AHI, the average value of complete and incomplete obstructed respiration per hour of sleep, and SAO2, the percentage of oxygen saturation). STUDY DESIGN:The study was conducted on 11 OSAS young subjects (mean age 6.9±1.04 years), all treated with rapid maxillary expansion (RME). Cardio-respiratory monitoring (8-channel Polymesam) was performed at the beginning (diagnostic, T0) and after 12 months of treatment. RESULTS:The mean values of cardio-respiratory parameters at TO were: AHI=6.09±3.47; SAO2=93.09%±1.60. After 12 months of treatment, the mean values of the same polysomnographic parameters were: AHI=2.36 ± 2.24;SAO2=96.81% ±1.60. These changes were associated with an improvement in clinical symptoms, such as reduction of snoring and sleep apnea. CONCLUSION(S):This study confirms the therapeutic efficacy of RME in OSAS young patients. This orthopedic-orthodontic treatment may represent a good option in young patients affected by this syndrome.