The atrial myocardium has been barely visible with thallium-201 myocardial scintigraphy. This is probably related to the difference in size, distance from anterior chest wall, and small coronary blood flow of the atrium, compared with the ventricle. We have encountered eight cases of visualization of the right atrial appendix (RAA). All had disease involving the right side of the heart, such as mitral stenosis (four cases), congenital heart disease (two), cor pulmonale (one), and primary myocardial disease (one). The RAA was identified from multiple projections in all cases and sometimes confirmed by radionuclide angiocardiography. The RAA was seen at the right upper aspect of the ventricles and was distinguishable from them. Evidence derived from ECG, chest radiographs, and cardiac catheterization, indicated that the most important factor in the visualization might be the displacement of the RAA to a more anterior position.