Maxillary advancement may result in movement of the posterior border of the hard palate with its soft palate attachment, which may cause impairment of velopharyngeal (VP) function. We examined VP function before and after Le Fort I osteotomy in 15 cleft lip and palate patients. The extent of maxillary advancement was measured by means of standard cephalometric radiographs taken before and after the operation. VP function was evaluated in terms of perceptual speech assessments, pressure-flow data and nasalance scores preoperatively and 2, 6 and 12 months after the operation. The results showed that maxillary advancement resulted in impairment of VP function in 4 (27%) of the patients.