The aim of the present investigation was to demonstrate whether children selected by their open lip posture show differences in their nasal airway resistance and facial morphology compared to children with closed lip closure. Thirty-two children with poor lip competence were compared to a control group of 20 with secure mouth closure. Patients with poor lip competence showed a significantly higher ML-NSL angle and also ML-NL angle. Anterior rhinomanometry, as well as measurements of the pharyngeal space on lateral headfilms, displayed no significant differences between the two groups. The same material was also grouped cephalometrically into skeletal open and skeletal deep bite configurations. The mean value of the nasal airway passage was lower in the skeletal open group, but not at a significant level.