OBJECTIVE: To test the hypothesis that there is no difference in mandibular rotation and angular remodeling between mouth-breathing (MB) children and nose-breathing (NB) children. PATIENTS AND METHODS: There were 56 MB children with severe obstruction (mean age, 6.1 years) and 56 NB children (mean age, 7.8 years). The cephalograms of each subject at baseline (T0) and after 1 year (T1) were traced and superimposed to determine the true and apparent rotations of the mandible and angular remodeling. Results MB children showed a significantly lower (p < 0.05) annual rate of angular remodeling than their NB counterparts (MB 0.19 vs. NB 0.85). However, there were no statistically significant differences between MB and NB children in true rotation (MB -0.68 vs. NB -1.27) and apparent rotation (MB -0.50 vs. NB -0.39). There was no association between the vertical facial type at T0 (mandibular plane-sella-nasion angle) and subsequent mandibular rotation or angular remodeling. CONCLUSIONS: Our investigation rejected the null hypothesis; in other words, angular remodeling in MB children is significantly less than that observed in NB children. However, there is no difference in mandibular rotation between MB and NB. Both groups showed the same counterclockwise mandibular rotation pattern, signifying that it is not possible to predict mandibular rotation in either NB or MB children on the basis on the vertical facial type.