Recent studies have shown that the Furlow double-opposing Z-plasty has several advantages that make it an attractive procedure for cleft palate repair and treatment of velopharyngeal insufficiency in selected cases. The anatomic changes associated with this procedure have never been documented prospectively. The purpose of this study was to describe radiographic dimensions of the velopharynx and aerodynamic measures of velopharyngeal function in a group of patients before and after Furlow Z-plasty for the treatment of velopharyngeal insufficiency. Twelve consecutive patients with cleft palate and velopharyngeal insufficiency, ranging in age from 3 to 19 years, were selected as candidates for Furlow Z-plasty based on perceptual, endoscopic, and radiographic findings. Eight patients had repaired cleft palate with a residual muscle diastasis and four patients had unrepaired submucous cleft palate. Subjects received aerodynamic and cephalometric assessments before and after Z-plasty. Cephalometric x-rays were measured for velar length, thickness, and pharyngeal depth. Mean nasal airflow during pressure consonants (Vn) was calculated from pressure/flow studies, and patients were categorized as having complete closure (<10 cc/sec Vn) or incomplete closure (>10 cc/sec Vn). After Z-plasty, there was a significant increase in velar length (p = 0.002) and velar thickness (p = 0.001). After surgery, patients with complete velopharyngeal closure had significantly greater velar length than the incomplete closure group (p = 0.05) with nearly twice the increase in length. Similarly, following surgery, the complete closure group had significantly greater thickness than the incomplete closure group (p = 0.01), with a greater postoperative increase in velar thickness (p = 0.005). Finally, there was a significant negative correlation between percent increase in length and percent increase in thickness for patients in the complete closure group (r = −0.91, p = 0.03). Findings demonstrate that following Furlow Z-plasty, patients with cleft palate and velopharyngeal insufficiency obtained significant increases in velar length and thickness. Greater velar length and greater velar thickness both were associated with complete velopharyngeal closure. Patients in the complete closure group tended to demonstrate large percent gains in either length or thickness or moderate gains in both. Patients in the incomplete closure group tended to demonstrate relatively small percent gains in both dimensions. Results suggest there may be important anatomic features (such as pharyngeal depth/velar length ratio) that can be evaluated before surgery to predict which patients may be most likely to benefit from Furlow Z-plasty as a form of treatment for velopharyngeal insufficiency.