Posttransplant lymphoproliferative disorder (PTLD) is a serious complication of organ transplantation and immunosuppression. Early diagnosis and treatment greatly affect prognosis. Chest radiographs (n = 13), chest computed tomographic (CT) scans (n = 2), or both (n = 20) from 35 patients with intrathoracic PTLD were retrospectively studied to define the intrathoracic manifestations of this disorder. Intrathoracic abnormalities consisted of pulmonary nodules (16 patients), patchy air-space consolidation (three patients), mediastinal and hilar adenopathy (17 patients), thymic enlargement (two patients), pericardial thickening and/or effusions (two patients), and pleural effusions (four patients). Multiple, well-circumscribed pulmonary nodules with or without mediastinal adenopathy are highly suggestive of PTLD. However, pathologic examination is usually necessary for a definitive diagnosis.