The authors report the cases of 2 patients who underwent lobectomy followed by irradiation for lung cancer and subsequently developed an aspergillus-infected cavity in the irradiated lung parenchyma. It is far from certain that aspergillosis must always develop in a pre-existing cavity. In cases where it developed on post-radiotherapy lung lesions, our 2 patients and a review of the literature encline us to believe that the fungus itself is responsible for the formation of cavities in lesions of radiation pneumonia. Treatment of such disease can only be surgical, and in spite of post-irradiation and post-surgery sclerosis, elective excision of the lesions is the best solution.