Closed chest trauma occasionally results in the development of traumatic lung cyst or pulmonary hematocele.Radiologically, this latter rarely mimicks posterior mediastinal mass, which can cause unnecessary surgicalresection, We encountered two cases of pulmonary hematocele simulating posterior mediastinal mass. Multiplicity ofthe lesion, fracture of surrounding bony structure, decrease of mass size at follow-up examination, an acute anglebetween the mass and chest wall, peripheral rim enhancement of the mass, as seen on CT scans, or characteristicsignal intensity suggesting hematoma, as seen on MR images, helped differentiate pulmonary hematocele fromposterior mediastinal mass.