The vast majority of pleural neoplasms invade the pleura secondarily and can be seen in patients with bronchogenic carcinoma, breast cancer, lymphoma, and ovarian or gastric carcinoma. Primary pleural neoplasms are less common, although they have developed notoriety since the up-surge of malignant mesothelioma and the knowledge of its connection to asbestos exposure. Other malignant primary tumors include localized fibrous tumor and pleural liposarcoma. In most patients with diffuse malignant pleural disease the chest radiograph shows pleural effusion with or without pleural thickening. Computed tomography (CT) usually provides precise localization and extent of the disease and may be of value in assessing chest wall and mediastinal involvement. In specific situations, magnetic resonance (MR) may be useful as a problem-solving tool when CT findings of chest wall or diaphragmatic invasion are equivocal or in patients with contraindication to intravenous administration of ionic contrast material.