Fifty seven-year-old male patient admitted to our hospital with complaints of swelling of the face, neck, arm and upper chest, dyspnea on exercise and dizziness. Facial oedema, cervical venous distension and collateral venous engorgement over the anterior chest wall were found in physical examination. Respiratory sounds were normal. Right-sided upper mediastinal widening was observed in chest radiography. A 5.5x3 cm sized anterior mediastinal solid mass compressing vena cava superior was detected on thoracic CT scan. Fiberoptic bronchoscopic findings were normal. A biopsy specimen was taken by right anterior mediastinotomy. Thymus originated small-cell carcinoma was reported on pathological evaluation. Any other focus of the tumor was not found. Owing malignant cells observed within the regressed thymus tissue, negative immunohistochemistry staining with leucocyte common antigen (CD45) and strongly positive chromogranine, the tumor was accepted as a primary thymic small-cell carcinoma. The patient was treated with six-course cisplatin+etoposide chemotherapy and chest irradiation. Initially, nearly complete tumor response was achieved. However, two years later a pancreatic metastasis emerged. He survived for 30 months after diagnosis.