A 67-year-old male patient came to the hospital due to lung cancer and mediastinal cystic mass which was suspected to be esophageal duplication cyst. Video-assisted thoracoscopic surgery (VATS) was performed and intra-operative finding suggested it as a cystic mass along the thoracic duct. Thoracic duct was ligated and the cyst was completely resected. A 48-year-old female patient visited the hospital for dysphagia. Mediastinal cystic mass was suspected to be an esophageal duplication cyst. Intraoperative finding suggest a thoracic duct lymphangioma. After thoracic duct ligation, the mass was completely resected with VATS. Postoperative chylothorax did not develop in both cases.