Introduction: Orthodontists frequently treat children with mouth breathing. The purpose of the present study was to examine dental positions, skeletal effects and the pharyngeal airway space of children with chronic allergic rhinitis, when compared with a control group exhibiting a normal breathing pattern. Material and Methods: Seventy Caucasian children from Santa Maria University Hospital - North Lisbon Hospital Center were evaluated, between September 2009 and February 2013. The study group comprised of 35 children with chronic allergic rhinitis, both genders, aged 5 - 14, with positive reaction to allergens, mouth breathing and malocclusion. The control group was composed of 35 children, both genders, displaying normal nasal breathing and malocclusion, who resorted to the orthodontic department. Measures of Ricketts, Steiner and McNamara's analysis were used and the t- Student test was applied to the data obtained. Results: Statistically significant differences were observed between the oral and nasal breathers, respectively: lower facial height (49.1/45.9 mm), Frankfurt - mandibular plane angle (30.1/26.9º) and Sela-Nasion - oclusal plane angle (17.3/15º), maxillary length (78.4/82.4 mm), mandibular length (102.4/107 mm), overbite (0.8/3.1mm) and overjet (4/4.7 mm). Discussion: Comparison between the allergic rhinitis and control group showed that there is an increased lower facial height, larger Frankfurt - mandibular plane angle and Sela-Nasion oclusal plane angle in children with chronic allergic rhinitis. This group also had a shorter maxillary and mandibular length, less overbite and decreased upper airway space. Conclusions: Children with allergic rhinitis and mouth breathing have longer faces, shorter maxillas and mandibles and a narrowed pharyngeal airway space. No statistical differences between the groups in sagital relationships or in dental inclinations were found.