Malignant diffuse mesothelioma is a tumour related to asbestos exposure, more common in males and located primarily in the chest cavity. Its diagnosis requires ruling out other tumours with pleural or peritoneal metastases, a biopsy showing a morphological pattern consistent with mesothelioma and in many cases to perform immunohistochemical markers to rule out an adenocarcinoma. We report here 20 cases of diffuse pleural mesothelioma and three cases of peritoneal mesothelioma in 20 males and three cases of peritoneal mesothelioma in 20 males and three females. Asbestos exposure was observed for 31% of cases. The most common clinical manifestations included headache and dyspnea; interestingly, three cases had hydropneumothorax with poor response to drainage. The diagnostic confirmation was obtained mainly with thoracotomy or laparoscopy biopsies and to rule out an adenocarcinoma immunohistochemical stainings were performed.