An intrathoracic gossypiboma is a rare condition. Moreover, intrathoracic gossypibomas with intrapulmonary location are extremely rare and only a few cases of intrapulmonary gossypiboma have been published. Usually gossypiboma has the characteristic CT appearance of a soft tissue mass with high attenuation, air bubbles and a whirl-like pattern, but its radiological manifestations may be variable according to the location and chronicity of the sponge. We report a case of intrathoracic gossypiboma initially misdiagnosed as an aspergilloma owing to its intrapulmonary location and air crescent sign on CT. In addition, our case will show morphological changes of the gossypiboma on CT during the 10 year follow-up period and correlate the CT findings with pathological results.