Esophageal duplication cysts are uncommon, benign lesions of the esophagus. They are rare congenital foregut anomalies. To be considered an esophageal duplication cyst, a lesion must meet the following criteria:1 the cyst in the esophageal wall 2 the cyst is covered with a muscularis propria,generally of two layers and 3 the cyst has an epithelial lining consistent with that of the 4 week embryo, which may be columnar or pseudostratified columnar, and may be ciliated. Herein we report a case of an esophageal cyst located within the thoracic cavity, which is, to the best of our knowledge, the first case reported in Korea. Surgery is generally the treatment of choice for esophageal cyst, and was indicated in this case for the diagnosis and management of symptoms attributable to the cyst.