Malignant mesothelioma of the pleura is a rare neoplasm with a poor prognosis. Noncharacteristic clinical signs, radiological features and similarity to other neoplasma (adenocarcinoma) in a microscopical evaluation lead to often diagnostic problems. Thoracoscopy followed by biopsy is routinely performed and is considered a main diagnostic procedure. Microscopic samples are usually examined by immunohistochemical analysis. In this report, presented is a case of malignant pleural mesothelioma, in which final diagnosis was delayed because of difficulties in diagnosis based on thoracoscopic biopsy.