Posttransplant lymphoproliferative disorder (PTLD) is one of the unfortunate complications of immunosuppression after allograft transplantation. 18F-FDG PET/CT plays an important role in the diagnosis and management of PTLD. The authors report a PET/CT scan of a young woman who received a heterotopic cardiac transplant, demonstrating 2 functional hearts in the thorax. The scan also demonstrates a small-volume mediastinal lymphadenopathy caused by the PTLD/B-cell lymphoma, subsequently proven by mediastinoscopic biopsy.