Post-transplantation lymphoproliferative disorder occurs in transplant recipients in whom immunosuppressive therapy has compromised the immune system. In patients who have undergone transplants, suppressor T lymphocyte function is suppressed, leading to unbridled B lymphocyte proliferation. We encountered a case with post-transplantation lymphoproliferative disorder which manifested as a focal hepatic mass in transplanted liver. This mass was isoechoic, with a peripheral hypoechoic halo on ultrasonogram, while on all three phases of helical CT scan, low attenuation without contrast enhancement was seen.