Molar-incisor hypomineralization (MIH), are enamel demarcated defects of systemic origin, affecting first molars and incisors. However, recent studies show that they can also affect other teeth and have genetic etiology, characteristics very similar to amelogenesis imperfecta (AI). Objective: To determine the dental, facial and skeletal characteristics present in individuals with MIH and compare them with the same characteristics present in individuals with AI, as an approach to a differential diagnosis. Method: 12 individuals between 7-10 years were diagnosed with MIH according to the European Academy of Pediatric Dentistry criteria, the Mathu Maju criteria, and the severity classification of Neeti Mittal. As a control group, 10 individuals with AI between 8-49 years were diagnosed according to the witkop criteria. Clinical examinations, extraoral photographs, lateral skull radiographs and study models were carried out for facial, dental and skeletal analysis. The information obtained was recorded in an Excel database and analyzed in the SPSS V.22 program. Results: Enamel defects in MIH were more frequent in posteriors than in incisors. In AI they were generalized. Apical Dilaceration and Taurodontism were more frequent in AI. In MIH, convex profile, skeletal class I, mandibular retrognathism, mandibular body rotation down and back (post rotation) and vertical growth were presented, coinciding in some characteristics with AI. None of the individuals with MIH presented hypodontia, oligodontia, gemination, fusion, concrescence, dent in dents, or acceleration of the root development. The measurements between MIH and AI statistically significant (P <0.05) were angle of the cranial base with palatal plane, mandibular ramus flexion and lower facial height. Conclusions: The main differences between the MIH and the AI were observed in the presence of dental anomalies and skeletal characteristics. Key words: hypomineralization, enamel, amelogenesis imperfecta, skull anomalies, phenotype.