Background. Rocabado’s hyoid triangle is the only cephalometric parameter that can assess the effects of orthodontic treatment on tongue posture. Aim. To evaluate the restoration of tongue posture and function by conducting a cephalometric assessment of the hyoid triangle before and after rapid maxillary expansion. Methods. Sixtyfour healthy patients aged 6-11 years with skeletal class II malocclusion, mixed dentition, and infantile swallowing took part in this study. They submitted to lateral cephalometric radiography before and after orthodontic maxillary rapid expansion, in order to assess the resulting changes in the proportions of the hyoid triangle (following Rocabado’s parameters). The cephalometric findings were compared according to sex, age, and divergence using the chi-square McNemar test at the 5% significance level (p<0.05). Results. The orthodontic treatment resulted an improvement from skeletal class II malocclusion to class I, with elimination of infantile swallowing in 81.8% of male patients [95% confidence interval (CI)=61.5–92.7%], in 87.1% of patients aged 6–7 years (95% CI=71.1–94.9%). Conclusions. This cephalometric analysis revealed that the hyoid riangle was modified by the orthodontic maxillary expansion, reconditioning of tongue posture and function particularly among male, aged 6-7 years old with skeletal class II malocclusion, mixed dentition, and infantile swallowing.