Local relapses in mediastinal non-Hodgkin's lymphomas in childhood are rare. Of the 15 children treated in our hospital during the last 11 years, 2 had early local or pleural relapses. At presentation both had extensive pleural effusions, and after completion of induction therapy still some fluid in the pleural space was present. A local irradiation was not performed initially. Be review of the literature for risks and benefit of local irradiation in mediastinal non-Hodgkin's lymphoma, local irradiation in children receiving aggressive chemotherapy should only be considered in few patients; preferentially in those, with incomplete disappearance of the mediastinal tumor or, as we may conclude from our patients, incomplete disappearance of pleural effusion.