OBJECTIVE: To test the hypothesis that there is no difference in cephalometric patterns among nose-breathing (NB) children and mouth-breathing (MB) children with different etiologic diagnoses. PATIENTS AND METHODS: There were 113 MB children and 113 NB children at the same stage of skeletal maturation (CS1 or CS2). MB children were divided into the following 3 groups: (1) MB children with nasopharyngeal obstruction caused by adenoid hypertrophy; (2) MB children with oropharyngeal obstruction caused by palatine tonsillar hypertrophy; and (3) MB children with oropharyngeal and nasopharyngeal obstruction due to adeno-tonsillar hypertrophy. All children underwent lateral cephalometric radiography; cephalometric measurements were taken to characterize the vertical facial pattern and the sagittal planes. RESULTS: All cephalometric measurements and proportions were significantly different in MB children when compared to NB children, except the SNB⁰. All comparisons between the three groups of MB children with the NB children showed a statistically significant difference. We also found a statistically significant difference among the 3 groups of MB children in the measures SNB⁰ NSGn⁰ and PFH/TAFH (posterior facial height/total anterior facial height). CONCLUSIONS: There are obvious differences in cephalometric measurements and proportions among MB children and NB children regardless of the cause of upper airway obstruction. Some cephalometric measurements differ among MB children according to cause. The mandible was positioned further anteriorly and superiorly in children with only palatine tonsillar hypertrophy, when compared with children who had adenoid hypertrophy.