We describe an adult patient with a large right atrial mass which was found to have the same echotexture as adjacent liver tissue on two-dimensional transesophageal echocardiography (2DTEE). By using live/real-time three-dimensional transesophageal echocardiography (3DTEE), we were able to examine the mass by meticulous cropping and confirm the echotexture was similar to liver tissue throughout its extent. Three-dimensional cropping also redemonstrated in a definitive manner that the mass was in continuity with liver. Thus, in our patient 3DTEE served to increase the confidence level of making a definitive diagnosis of a supernumerary lobe of liver. To the best of our knowledge, the incremental value of 3DTEE over 2DTEE in diagnosing a supernumerary liver lobe has not been reported previously. The mass was surgically resected and the findings confirmed as liver tissue by pathological examination.