The authors report a 4-year-old male with Hodgkin's disease with atypical clinical presentation, laboratory data and imaging studies as well as an increased radiosensitivity. These were the first symptoms which raised the suspicion of ataxia-telangiectasia. The lymphoma presented as a solid tumor mass in the right upper posterior mediastinum without peripheral lymphadenopathy. The alpha-fetoprotein was significantly increased and the diagnosis of a germ-cell tumor or neuroblastoma was suspected. After partial resection of the tumor the histology indicated Hodgkin's disease-mixed cellularity. The boy received chemotherapy according to DAL HD-95 protocol without any unusual toxicity. Low-dose radiation therapy of the upper and middle mediastinum was followed by early radiation-induced esophagitis and appearance of a large pericardial effusion one year later. Ataxia and bulbar and skin telangiectasias at the radiation site appeared in the next years. He suffered recurrent pulmonary infections and succumbed to severe pneumonia with respiratory failure and pulmonary hypertension five years after the diagnosis of malignant lymphoma without evidence of recurrence of Hodgkin's disease.