Mediastinal cysts, described also as homoplastic dysembryomas, account for 20% of mediastinal lesions. There are bronchogenic, oesophageal, gastrogenic and enterogenic, pericardial, non-specific cysts and cystic lymphangiomas. The authors present 6 patients with mediastinal cysts from a total number of 96 patients with mediastinal tumours subjected to surgery during a 14-year period (from Jan. 1 1987 to Dec. 31 2001). The group comprised 5 adults and one child. In four patients the authors selected thoracotomy as the route of access to the mediastinum, in one instance total sternotomy and once upper partial sternotomy. The cysts were removed as a whole. Histological examination revealed in four patients the diagnosis of a bronchogenic cyst, once a connective tissue cyst with respiratory epitheliumm and once a cyst lined with squamous epithelium. The postoperative course was in all patients free from complications. In the conclusion the authors emphasize the importance of complete removal of mediastinal cysts as relapses occur if part of the secretory eoithelium is not removed.