Traumatic pulmonary pseudocysts (TPPs) are rare sequelae of blunt chest trauma. We present a retrospective review of TPPs observed in our hospital and discuss the diagnosis, treatment, and complications of these unusual lesions. Between 1991 and 1999, 11 TPPs were diagnosed in 10 patients. None of the lesions was detectable on the chest radiograph obtained on the day of injury. In contrast, computed tomographic scan of the chest always demonstrated the TPPs. In nine cases, spontaneous healing of the lesions was observed. One patient with a large lesion of the left lower lobe developed significant endobronchial bleeding and underwent successful emergency lobectomy. TPPs are often missed by chest radiography, particularly when it is obtained in the supine position, whereas computed tomographic scan allows the identification of these lesions in all cases. TPPs are self-limiting, benign lesions that usually require no specific therapy. Surgical treatment is indicated in rare instances and only when complications occur.