Radiotherapy is still one of the effective means for treatment of malignant tumors up to now. Particularly, it is an indispensable effective measure for treatment of some lymphoma patients. In routine work, radiation pneumonitis (RP) is the most significant complication of acute treatment-related toxicities in lung cancer; however, serious radioactive pneumonia is rare for the radiotherapy of neck lymphoma because the volume of the lungs affected by radiation dose was very small. We report a lymphoma case, where the patient had undergone radiotherapy for the bilateral neck and bilateral supraclavicular/infraclavicular area. Following completion of radiotherapy, the patient developed severe radiation pneumonitis.