In right lobe living donor liver transplantation (RL-LDLT), venous reconstruction of large middle hepatic vein (MHV) tributaries is often necessary. However the standard for reconstruction is unclear. In two recent RL-LDLT cases, we reconstructed a MHV tributary after estimating the donor's liver volume by three-dimensional images using helical computed tomography (3D-CT). 3D-CT demonstrated that the expected donor right lobe volume was 437 ml, which represented 46.2% of graft volume/recipient's standard volume ratio (GV/SV ratio) in case 1, and 600 ml (46.4%) in case 2. Moreover, 3D-CT revealed a large MHV tributary, 8 mm in diameter, drained 190 ml in volume of segment 8 in case 1, and, 7 mm in diameter, drained 138 ml in case 2. In these cases, when the area drained by the MHV tributary was excluded, GV/SV ratio were 26.1% and 35.7%, respectively. Based on this data, we reconstructed a large MHV tributary in both cases.