The current study aimed to examine the effects of the modified tandem appliance on the dimensions of the airways. Pretreatment and post-treatment cephalograms of twelve patients with maxillary deficiency, (7 girls, 5 boys; mean age 8±0.5 years), who were seeking treatment at the Department of Orthodontics, Damascus University, were studied. These patients were treated using the modified tandem appliance with rapid maxillary expansion.