Intrathoracic splenosis is a rare diagnosis that is usually made following an invasive procedure. Although radiographic and CT findings are nonspecific, these findings combined with a history of splenic injury should suggest the possibility of this diagnosis. We present a patient with intrathoracic splenosis diagnosed on the basis of a technetium Tc 99m heat-damaged RBC scan following false-negative technetium Tc 99m sulfur colloid scan results.