We reported a case of primary cardiac lipoma in a 74-year-old woman who had a 23-year history of cardiomegaly. The chest roentgenogram showed an enlargement of the cardiac silhouette. The electrocardiogram showed slight abnormalities including mild low voltage of R wave in V6 and flat T wave in V5 and V6. M-mode and cross-sectional echocardiography revealed a low echoic mass which mainly situated between left ventricular posterior wall and the pericardium. The left and right ventricular wall motion was not affected. Computed tomography of the heart revealed a large mass backward of the left ventricle and right side of the right atrium. The attenuation values of the mass ranged around-118HU and was compatible to lipoma. We diagnosed as a lipoma of the heart possibly arising from the pericardium. Computed tomography may be of use for a very specific diagnosis of cardiac lipoma.