Cases Description: The posterior crossbite caused by transverse maxillary endognatia is one of the most prevalent malocclusions in the deciduous and mixed dentition. The aim of this study is to highlight the importance of the early treatment of maxillary endognathia. Two clinical cases are described, treated in deciduous dentition, with the use of transversal expansion of the maxilla, with different therapeutic approaches. Case 1: A 5-year-old male patient was recommended by the pediatrician to evaluate the dentition. Case 2: A 4-year-old male patient appeared at the clinic to perform a routine evaluation. In both cases: clinical history, clinical examination and complementary x-ray were performed: orthopantomography, lateral teleradiography, study models and photographs. Diagnosis: Bilateral maxillary endognatia with functional deviation to the left at the closure and lateral and posterior left crossbite in position of maximum intercuspation. Case 1: Treatment performed with a Hawley Expander with posterior bite planes. Case 2: Treatment with a fixed device - Quad-Helix. Discussion: Clinical success was achieved in both cases. In the first case, a removable device with posterior bite planes was used to promote neuromuscular re-education. In the second case we used a fixed appliance since we were warned by the mother about the probable lack of cooperation with a removable one. At the end of the active treatment, the child was followed up by the speech therapist for neuromuscular re-education. Conclusions: Early correction of unilateral posterior crossbite improves functional changes and eliminates morphologic and functional asymmetries of the mandible. Keywords: pediatric dentistry, orthodontic appliances, crossbite, malocclusions