Problems in the transverse plane of space are seen primarily as posterior crossbites, which may be due to displacement of teeth relative to their supprting bone (dental crossbite), or to a narrow maxilla or wide mandible (skeletal crossbite). It is important to specify, in the sense of the location of the anatomic abnormality, why the crossbite exists. Where a maxillary expansion may be considered as part of a treatment aiming to coordinate the mazillary and mandibular arches. For thr correction of maxillary skeletal constriction, rapid maxillary expansion procedure (RME) is indicated. In this case report, the evaluation of P-A cephalo-grams before, after RME, and after active treatment will serve as a focus.