Introduction: Mouth breathing is a habit that occurs in most children and can cause changes in craniofacial and occlusal development.

Objective: To analyze the aetiology of mouth breathing, the effects it has on dental occlusion and craniofacial development, as well as its treatment.

Methodology: An extensive literature search was carried out in the PubMed, SCOPUS and Google Scholar databases, analyzing the keywords: mouth breathing, craniofacial development, occlusal development, aetiology and treatment.

Results: The aetiology of mouth breathing is attributed to inflammatory, anatomical and obstructive factors, the latter being the main cause of mouth breathing. Its main effects on occlusion are an increased facial height and overjet together with an inclined occlusal plane. Alterations of mouth breathing in craniofacial development are abnormal transverse and vertical growth and backward and downward rotation of the maxilla and mandible. Treatment can be by rapid expansion, myofunctional therapy, surgically and by pharmacological treatment.

Conclusion: Mouth breathing is an anomaly that can be caused by an obstruction of the upper airway, and can cause occlusal problems and a deviation of craniofacial development, so it is important to correct it early and in a timely manner.