While the data regarding radiotherapy (RT)-induced cardiovascular disease in lung cancer patients is limited, the cardiotoxic effects of RT have been thoroughly documented in long-term survivors of breast cancer and Hodgkin's disease. Herein we review data illustrating the cardiotoxic effects of thoracic RT in lung and breast cancer patients. Older RT techniques for treating the breast/chest wall and draining lymph nodes resulted in a relatively high dose being delivered to a substantial volume of heart, and convincing evidence exists of excess cardiovascular morbidity and mortality in patients treated with these techniques. While modern RT techniques have reduced radiation exposure to the heart, they have not eliminated it. In patients treated with modern techniques, there are conflicting data regarding the impact of radiation on late cardiovascular morbidity and mortality. Thus, it is prudent to reduce cardiac exposure as much as possible. Techniques to reduce further cardiac exposure (eg, respiratory gating, intensity modulated radiation therapy) are currently under investigation. Further work is needed to quantify the frequency and severity of cardiac injury and develop preventative methods.