Respiratory disorders in the upper respiratory tract during sleep are most often part of a continuous pathological process of long standing. Schematically, three clinical syndromes with increasing severity are described: breathing with the mouth open, snoring and sleep apneal hypopnea syndrome. Obstructive sleep apnea syndrome (OSAS) is a subtle, but severe sleep disorder of early childhood. It is often difficult to detect and may have long-term consequences, including failure to thrive, behavioral disturbances, developmental delay, and cor pulmonale. These conditions always include a functional maxillofacial perturbation, which may be associated with a constitutional or acquired morphological disorder. Pediatric dentists must be aware of the problems connected with mouth breathing and OSAS (obstructive sleep apnea syndrome) in children as any delay in diagnosis and treatment may cause prolonged morbidity. They also have a role in the diagnosis and co-management of these patients because the signs and symptoms may be recognizable in the dental practice. Besides the medical approach itself, the treatment sometimes is surgical, always orthopedic: the earlier it is initiated, the more effective, simple and unrestraining it is. The aim of this work is to focus attention on the early diagnosis and prevention of these pathologies. Diagnostic guidelines will be illustrated.