BACKGROUND Partially unroofed coronary sinus (PUCS) is a rare congenital cardiac anomaly and prone to be misdiagnosed. The purpose of this study was to explore the value of transesophageal echocardiography (TEE) in CS imaging for the detection of PUCS and to develop a special two-dimensional TEE-based en face view of CS. METHODS Twenty adult patients with suspected PUCS, showing a dilated coronary sinus and an enlarged right heart on transthoracic echocardiography (TTE), underwent TEE examination. In the mid-esophageal plane and close to an angle of 120°, the en face view of the CS successfully imaged the roof of the CS, which was beyond the realm of the atrial septum, and the interatrial septum was obtained simultaneously in the same view. Meanwhile, the 3D zoom mode could clearly display the comprehensive volume image and the adjacent structures of the PUCS. The results of TEE were compared with the findings of surgery or catheterization. RESULTS En face view of the CS was obtained successfully by 2DTEE in 20 patients. In addition, 3DTEE was used for imaging of PUCS in 11 of the 20 patients. PUCS was ultimately confirmed in 13 patients either by surgery or catheterization. The TEE for PUCS diagnosis was consistent with the surgical findings. CONCLUSIONS Transesophageal echocardiography can be successfully applied to obtain the comprehensive view of CS and its surrounding structures. The en face view of CS provided by 2DTEE may be helpful in better understanding PUCS and discriminating it from associated atrial septal defects.