Nasal-breathing impairment has been described as a possible determinant of maxillofacial development in children with adenoids/tonsils hypertrophy. However little is known about the possible influence of nasal septum deviation on craniofacial growth in childhood. We conducted a multicenter cephalometric study to compare skeletal and dental features in children with chronic nasal-breathing obstruction secondary to nasal septum deviation and nose-breathing controls. Ninety-eight children (59M, 39F; mean age 8.8 years; age range 7-12 years) with obligate mouth-breathing secondary to nasal septum deviation (group 1) and 98 age- and sex-matched nasal-breathing controls (group 2) were evaluated. Nasal-breathing function was assessed in all patients with clinical history, ENT instrumental examination and anterior active rhinomanometry. Cephalometric parameters were recorded in all subjects. Patients of group 1 showed a statistically significant increase of upper anterior facial height (N-palatal plane) and total anterior facial height (N-Me) with regards to group 2. The angular relationships of the sella-nasion, palatal, and occlusal planes to the mandibular plane were greater in group 1 in comparison to controls. The gonial angle (Ar-Go-Me), palatal height and overjet were significantly higher in the mouth-breathing group. A significantly retrognatic position of the maxilla and mandible was recorded in group 1 in comparison to group 2. Most mouth-breathing children showed class II malocclusion, while the majority of control subjects presented normal occlusion. The prevalence of cross-bite was higher in group 1 with respect to controls (p=0.02). Children with obligate mouth-breathing due to nasal septum deviations show facial and dental anomalies in comparison to nose-breathing controls. Possible physiologic explanations of our findings are reported. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.