Abstract: Objective To discuss the security, effectiveness and risk factors of videoassisted thoracoscopic surgery for posterior mediastinal tumors. Methods We retrospectively analyzed the data of 59 patients including 36 men and 23 women who underwent thoracoscopic resection of posterior mediastinal tumors in People’s Hospital of Peking University from May 2001 to July 2009. Their age ranged from 6 to 73 years old with an average age of 40.6 years old. The average maximum diameter of the tumors was 4.86 cm. All procedures were performed under general anesthesia and tumors were cut out with three ports. The anterior port was extended to 6 to 10 cm when conversion to thoracotomy was needed. After mediastinal pleura were opened, the tumor was stripped out along the outside of peplos and the vascular pedicle nerves were managed respectively. Results All surgeries were carried out successfully. The surgical duration, perioperative blood loss, postoperative chest tube duration and postoperative stay in hospital were respectively 45-300 min(125.80±57.40 min), 10-1 000 ml(168.10±157.70 ml), 1-10 d(2.50±1.74 d), and 2-14 d(5.24±2.24 d). There were 6 cases of conversion to open thoracotomy with a conversion rate of 10.2%. Postoperative pathology showed that there were 46 cases of neurogenic tumors, 10 cases of cyst, 2 cases of teratoma, and 1 case of lipoma. Follow-up was done on 51 cases for a period of 7-108 months(55.0±24.0 months) and 8(13.6%) cases were missed out during the period. No recurrence or death occurred during the followup. Logistic multivariable analysis showed that maximum diameter of the tumor ≥6 cm was the independent risk factor for extending operative time (OR=1.932，P=0.004), increasing perioperative blood loss (OR=2.267，P=0.002), increasing conversion rate to thoracotomy (OR=3.123，P=0.004) and increasing postoperative complication rate (OR=1.778，P=0.013). Conclusion Videoassisted thoracoscopic surgery for posterior mediastinal tumor is safe and effective. Maximum diameter of the tumor ≥6 cm is an independent risk factor for increasing operation difficulty and risk.