Radiation therapy alone to the nodal drainage sites above the diaphragm, namely a "mantle" field, is often standard treatment for early stage Hodgkin's disease and may be used in combination with chemotherapy in more advance disease. Localised pneumonitis and fibrosis are recognised treatment related sequelae; however, other pulmonary complications, including pneumothorax, have been described. Two cases of spontaneous pneumothorax following mantle radiation therapy are presented.