OBJECT Focal cortical dysplasia (FCD) is one of the most common causes of intractable epilepsy leading to surgery in children. The predictors of seizure freedom after surgical management for FCD are still unclear. The objective of this study was to perform a volumetric analysis of factors shown on the preresection and postresection brain MRI scans of patients who had undergone resective epilepsy surgery for cortical dysplasia and to determine the influence of these factors on seizure outcome. METHODS The authors reviewed the medical records and brain images of 43 consecutive patients with focal MRI-documented abnormalities and a pathological diagnosis of FCD who had undergone surgical treatment for refractory epilepsy. Preoperative lesion volume and postoperative resection volume were calculated by manual segmentation using OsiriX PRO software. RESULTS Forty-three patients underwent first-time surgery for resection of an FCD. The age range of these patients at the time of surgery ranged from 2 months to 21.8 years (mean age 7.3 years). The median duration of follow-up was 20 months. The mean age at onset was 31.6 months (range 1 day to 168 months). Complete resection of the area of an FCD, as adjudged from the postoperative brain MR images, was significantly associated with seizure control (p = 0.0005). The odds of having good seizure control among those who underwent complete resection were about 6 times higher than those among the patients who did not undergo complete resection. Seizure control was not significantly associated with lesion volume (p = 0.46) or perilesion resection volume (p = 0.86). CONCLUSIONS The completeness of FCD resection in children is a significant predictor of seizure freedom. Neither lesion volume nor the further resection of perilesional tissue is predictive of seizure freedom.