Mediastinal irradiation for cancers, mainly breast cancer and Hodgkin's disease, has numerous potential adverse effects, including coronary artery disease, pericarditis, cardiomyopathy, valvular disease, and conduction abnormalities. The prevalence of valvular dysfunction is relatively low, and regurgitation is more common. We report the case of a 58-year-old woman with severe radiation-induced mitral stenosis and discuss the potential additional value of three-dimensional transesophageal echocardiography.