Intrathoracic involvement is common in both Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). The most common manifestation is mediastinal lymphadenopathy. In HD, nodal involvement is by contiguity and usually involves the superior mediastinum, while the findings in NHL are more variable. Pulmonary parenchymal disease occurs in 38% of HD and 24% of NHL. In untreated HD, parenchymal involvement is invariably associated with mediastinal lymphadenopathy and often with widespread disease. Three distinct radiological patterns of pulmonary lymphoma are recognised: nodular, bronchovascular-lymphangitic and pneumonic-alveolar. Rarely lymphoma may be endobronchial. Pleural effusion occurs in 16% of lymphoma patients and is usually associated with disease elsewhere. It is frequently caused by lymphatic obstruction but may be due to direct pleural involvement by tumour. Chylothorax may occur in NHL but is unusual in HD. Diagnosis of intrathoracic lymphoma is by transbronchial or transthoracic biopsy or by needle aspiration of tissue or pleural fluid. The addition of immunostaining improves the diagnostic yield in equivocal cases. Treatment and prognosis vary depending on cell-type, location and extent of disease.