A 58-year old woman was referred because of progressive heart failure since three weeks. Because of peripheral oedema and the presence of a diastolic murmur an echocardiography is performed showing a mitral stenosis and the presence of a thrombus in the left atrium. We present 3-D Computed Tomography (CT) images that show the massive extent of the left atrial thrombus only sparing the ostia of the pulmonary veins. A clue for diagnosis for mitral stenosis is the presence of an rumbling mid-diastolic murmur.