Pycnodysostosis is a rare clinical entity, first described in 1962 by Maroteaux and Lamy. It is a genetic disorder, usually diagnosed at an early age. However, the diagnosis is sometimes late, made as a result of bone fracture, given the severe bone fragility resulting from increased bone density. Oral and maxillofacial manifestations of this disease are very clear. The head is usually large, the nose beaked, the mandibular angle obtuse, and both maxilla and mandible hypoplastic. Dental abnormalities and impaction are observed, as well as alterations in eruption and frequent dental crowding. The differential diagnosis is established with osteopetrosis, cleidocranial dysplasia and idiopathic acro-osteolysis. This article reviews the clinical and radiographic characteristics of pycnodysostosis based on three clinical cases of patients with this disease.