Dentigerous cysts are characterized by slow and non-symptomatic growth. Usually they are recognized accidentally during the radiological examination of patients with an occlusion defect or dental age different than growing age. In the case described, the patient presented for dental treatment with the complaint of an occlusion defect and the appearance of a right deciduous maxillary lateral incisor (52). Radiological examination showed the presence of a horizontally positioned maxilla right lateral incisor (12) and dentigerous cyst of tooth 13 (right canine) in the maxilla sinus. After surgical consultation the cyst enucleation and extraction of the unerupted maxillary right canine were performed. Four months later the orthodontic treatment began.