The aim of this research was to evaluate the effect of the Delaire surgical technique on the midfacial morphology in a group of subjects with a congenital unilateral cleft of lip and palate (UCLP), prior to orthodontic treatment. Thirty-five UCLP (15 left and 20 right) patients (16 males and 19 females, mean age 7.03+/-0.9 years; age range 8.7-5.0 years), treated for the correction of congenital malformation, were retrospectively selected. Analysis of midfacial growth was undertaken on lateral cephalograms, and the data were compared with reference values (Ricketts analysis). A Mann-Whitney ranked sum test was used to detect significant differences between the findings and reference values. P <or= 0.05 was considered as significant. The results demonstrated a retropositioning of both the maxilla and mandible (SNA and SNB P<0.01) and increased mandibular development (Go-Me distance). Vertically, there was a trend to a posterior rotation of the mandible (P<0.01), resulting in a hyperdivergent profile. This trend was confirmed by the increase in SpA-SpP/Go-Me (P<0.05). In agreement with previous studies, the effects of surgical closure of a cleft lip might be responsible for excessive maxillary retropositioning with a downward rotation.