The purpose of our study was to evaluate the vertical, saggittal and transversal effects of Nitanium Palatal Expander and Quad-helix appliances on dentofacial structures in patients with maxillary transversal defficiency and posterior cross-bite. The study was carried on lateral, frontal and occlusal radiographs and orthodontic models of 22 patients within the average age of 12.7 years who manifested with bilateral posterior cross-bite. The measurements obtained from radiographs and models were evaluated statistically by Wilcoxon and Mann-Whitney U tests. In conclusion, significant amounts of expansion were observed in both groups. Along with the advantages of application and activation, treatment time had shortened and more pronounced skeletal effects was observed in NPE group when compared with the Quad-helix group.