The authors have examined a series of 992 patients with non-Hodgkin lymphomas treated at the National Cancer Institute of Milan from 1966 to 1977. The pulmonary parenchymal lesions were studied. The lung involvement by lymphomas is unusual and show a difficult X-ray diagnosis. A classification deriving from the experience of the various roentgenologic findings is proposed. Furthermore the most important differential diagnostic difficulties, some of which have an impossible solution even with the most recent X-ray techniques, are analized.