INTRODUCTION: Pharyngeal flap surgery is a widely used procedure for surgical management of velopharyngeal insufficiency. OBJECTIVE: To investigate the effect of pharyngeal flap surgery on the dimensions of the nasal airways. MATERIALS AND METHODS: We evaluated 52 patients of both genders (mean age, 17 years) with repaired cleft palate (isolated only) and residual velopharyngeal insufficiency. Participants underwent aerodynamic evaluation of breathing (pressure-flow technique) before pharyngeal flap surgery and, on average, 12 months after surgery (post) to determine the minimal cross-sectional nasal area. The nasal area was estimated during breathing at rest by means of pressure and flow measurement as described by Warren and Dubois (1964). The pre- and postoperative measurements were compared individually by calculating the difference between them (NApost − NApre). Individual variations between pre- and postoperative measurements were considered clinically significant when >10%, which corresponds to the error inherent to the method, as stated by Watzke et al (1990). RESULTS: It was found that 64% (33/52) of patients had significant reduction of nasal airway dimensions after pharyngeal flap surgery. CONCLUSION: Pharyngeal flap surgery modifies nasal airway dimensions. The reduction of the nasal airway dimensions in a significant proportion of patients undergoing pharyngeal flap surgery highlights the importance of postoperative evaluation and follow-up in these cases. In addition, the pressure-flow technique is a reliable method to analyze the effect of pharyngeal flap surgery on the upper airways.