Traumatic pulmonary cysts are rare cavitary pulmonary lesions following nonpenetrating thoracic trauma. The pathogenesis of this lesion Is a tear in the pulmonary parenchyma with leakage of air and fluid into this tear. The diagnosis is one of exclusion, based on an awareness that lung cyst can develop after trauma. Once traumatic lung cyst is diagnosed, the principle of the treatment is in-hospital obser- vation with respirato y support. However, if a cyst is complicated by infection unresponsive to a trial of appropriate antibiotic therapy and does not progressively become smaller, surgical intervention is indicated. Authors recently experienced a case of traumatic lung cyst in a 19 year-old man. Case presentation and review of articles on traumatic pulmonary cyst follows.