Objective. To evaluate the relationships between anatomical changes and treatment outcomes after velopharyngeal surgery in obstructive sleep apnea (OSA) patients with small tonsils (grade 0-2 on the Brodsky scale). Study Design. Case series with planned data collection. Setting. University medical center. Subjects and Methods. Thirty-six OSA patients with small tonsils underwent velopharyngeal surgery including revised uvulopalatopharyngoplasty with uvula preservation and transpalatal advancement pharyngoplasty. Pre-and postoperative upper airway 3-dimensional computed tomography and polysomnography findings were obtained for comparison and analysis. Results. The overall apnea hypopnea index (AHI) decreased from 56.8 (interquartile range, 37.5-70.1) preoperatively to 16.1 (10.8-33.5) postoperatively (P < .001). The change in minimal cross-sectional area of the velopharynx (VmCSA) was independently associated with the change in AHI (P =.001, R-2 = 0.271). Preoperative VmCSA was the only preoperative anatomical variable that was an independent predictor of change in VmCSA (P =.009, R-2 = 0.184). Postoperative VmCSA was independently associated with postoperative AHI (P < .001, R-2 = 0.341). Conclusion. In patients with small tonsils, an adequate increase in VmCSA is associated with a successful outcome after surgery. Patients with a relatively small preoperative VmCSA are more likely to have favorable anatomical changes after surgery.