Objective: Cyclooxygenase-2 (COX-2) has been claimed to play role in carcinogenesis and be related to a bad prognosis in tumours. The aim of this study was to investigate the relationship between COX-2 expression and clinical and pathological parameters in early and advanced stage lung cancer patients. Materials and Methods: A total of 73 patients with lung cancer (27 adenocarcinomas, 33 squamous cell carcinomas, 4 large cell carcinomas and 9 small cell cancer) were analysed retrospectively. COX-2 expression was evaluated by immunohistochemistry in resection materials or lung biopsies. Tumor cells demonstrating more intense staining than smooth muscle and endothelial cells were recorded as COX-2 positive. We investigated the correlation between increased COX-2 expression and histological type of the tumor, the stage of the disease and survival. Results: COX-2 expression was observed in 55% of the adenocarcinomas, 45% of the squamous cell carcinomas and 22% of the small cell carcinomas. No correlation was apparent between COX-2 expression and disease stage, histological type and the survival. Conclusion: The results of this study do not support COX-2 expression as an independent prognostic factor in lung cancer. However, since results of the literature are different, further studies made in larger series are needed.