Adenoid facies is a disorder which refers to the open-mouthed face of children who have long faces with adenoid hypertrophy. Hypertrophy of the lymphoid tissues in the throat (the adenoids) is the most common cause of nasal obstruction in children. The mouth is always open because upper airway congestion/narrowing has made patients obligatory mouth breathers. Persistent mouth breathing is seen due to nasal obstruction in children and it may be associated with the development of craniofacial anomalies such as the adenoid facies (also called the “long face syndrome”). The most common symptoms are habitual mouth breathing and snoring. The most dangerous symptom is sleep apnea due to obstruction. This article discusses the orthodontic aspects of diagnosis and treatment of adenoid facies.