Thoracic duct cysts are very rarely observed cysts of the mediastinum. These cysts, which can become established in the costovertebral sulcus or the visceral compartment, have generally been reported at the level of the 10th and 11th vertebrae; however, they can be observed at any location along the ductus [11, A 37-year-old male patient complained of chest pain for the last 3 months that especially increased after meals. He complained of shortness of breath while walking or going up the stairs, for the last month. The lung graphy showed an increased darkening at a 5x6cm smooth (clean-cut, regular, orderly) bordered shadow just behind the heart shadow. The patient's computed thorax tomography showed a retrocardiac-paravertebral, middle line positioned, 8.5x7x6 cm proportioned, regular bordered, thin walled, homogenous cystic bulk at the subcarinal level. The patient, who could not be relieved with medical treatment, was taken to surgery. The lesion was reached by right posterolateral thoracotomy, and drainage of lymph-containing cystic fluid and excision of the cyst walls were performed by incising the thoracic duct cyst with a mediastinal pleura incision. Mass ligation was then performed to the thoracic duct. We wanted to present our thoracic duct cyst case in this article due to the currently limited number of actual cases reported in the literature.