Class III malocclusion usually becomes manifested at a very early age, most typically evidenced clinically by the appearance of either an edge-to-edge incisor relationship or an anterior crossbite. Anterior crossbite, by it-self, retards growth of maxilla, and accelerates growth of mandible. So, treatment should be started as early as the patient cooperates, removing any factors or forces that inhibit growth and development in the same physiologic maxillary displacement direction. The facial mask is effective in most developing Class III patients, because the appliance system affects virtually all areas contributing to a Class III malocclusion. Thus, the facial mask can be applied to most developing Class If cases regardless of the specific etiology. In these cases, the results were followed. Anterior crossbite was corrected by anterior movement of maxilla and downward backward rotation of mandible and simultaneously, lower facial height was increased. So, it can be concluded that the facial mask is effective in treating growing patients with a deficient maxilla.