Compare the maxillary growth of patients with Unilateral Cleft treated with pre-surgical Functional Maxillary Orthopedic (FMO) and that of who underwent a surgical procedure with no previous use of appliances. Prospective study, the patients were divided into 2 groups. G1, was composed of 12 patients who received no pre-surgical intervention and cheilorhinoplasty at 6 months of age and G2, included 12 patients treated using Pre-Surgical Funtional Maxilary Orthopedic; they underwent no surgery during the study. Measurements were taken at three times: before the first month of life, at 6 months and between 9-12 months of age. Cleft distance (anterior, medium and posterior), maxillary width (anterior, medium and posterior) and minor and major segment width were analyzed. Alveolar Cleft decrease was 79.82% in G1 and 52% in G2. Posterior Cleft decrease was 24.1% in G1 and 41.77% in G2. Greater Segment Width increase was 24.53% for the patients in G1, and 37.47% for the patients in G2. As for Inter Canine Width, a decrease of 5.16% in G1 and an increase of 9.19% in G2 were found. Medium Arch Width only increased in a statistically significant manner in G2 9.02%. Surgery allowed for the closure of the alveolar cleft. FMO made it possible to close the anterior and the posterior clefts through the growth of the maxillary segments, increased the transverse growth of the maxilla and could prevent maxillary collapse. Each team must individually evaluate whether to indicate or not the use of preoperative orthopedics.