Radiological documentation, especially lateral head X-rays, are used in planning orthodontic therapy. They image both hard and soft tissues, and can be used for the initial assessment of the upper respiratory tract, which anatomically extends from the anterior nares to the larynx. Patients with Down syndrome is often a study group in which various disorders are diagnosed, including 30–55% of cases with obstructive sleep apnea, which may be caused by narrowing of the upper respiratory tract. A decrease in the size of the upper respiratory tract is observed in children with Down syndrome compared to healthy children, which may predispose them to respiratory problems. The influence of the anterior-posterior position of the mandible on the size of the upper respiratory tract in Down syndrome is observed.

Key words: lateral head X-rays, upper respiratory traks, Down syndrom, cephalometric analysis.