The authors report two cases of differentiated carcinoma of the thyroid with pulmonary involvement showing as miliary shadowing radiologically which preceded the diagnosis of the thyroid neoplasm by 35 and 6 years respectively. The two patients had undergone cervical radiotherapy in infancy for lymphadenopathy whose aetiology had not been determined. The scintigraph with iodine 131 showed tht in two cases there was a bilateral and diffuse pulmonary uptake in keeping with pulmonary lesion of metastatic origin. Our observations recall the possibility of a slow evolution of pulmonary metastases and carcinoma of the thyroid and the role of cervical irradiation in the development of such cancers. With miliary shadowing a metastatic origin, in particular that of the thyroid, should be considered and in the majority of cases the proof could be supported using iodine 131 scintigraphy. The delay in appearance of pulmonary metastases during the course of cancer of the thyroid is variable. They occur most often after the initial diagnosis or more rarely preceding the discovery of a primary thyroid cancer. The pulmonary metastases may be asymptomatic. This neoplasm may benefit from a specific effective therapy and prolonged remissions have been described even with metastases.