This article presents three cases of carcinosarcoma of the lung which is considered to be a rare neoplasm. The authors describe supposed etiology, clinical symptoms, preoperative diagnostic difficulties, surgical interventions performed, postoperative course and follow-up. The role of modern histopathological techniques like use of monoclonal antibodies reaction against keratin, vimentin and neurofilaments in differential diagnosis is emphasized. Short review of other authors reports is presented.