When unilateral mandibular growth disturbances appear early in childhood, they usually lead to maxillomandibular deformities. Facial asymmetry, mandibular retrusion, and malocclusion are signs also found in hemifacial microsomia. Some of these patients develop an obstructive sleep apnea syndrome, which can be resolved by surgical-orthognathic treatment. Pre and post-operative polysomnograms with recording of oxygen saturation are objective measures of good surgical results. Two patients with facial asymmetry and obstructive sleep apnea syndrome are presented. Special emphasis is made on treatment planning.