Purpose: Hypertrophic osteoarthropathy(HOA) is a clinical syndrome consisting of clubbing, periostitis and synovitis. Most frequent causes of hypertrophic osteoarthropathy are intrathoracic neoplasms, among which the bronchogenic carcinoma ranks the highest. But computed tomographic evaluation of intrathoracic neoplasm associated with HOA has been seldom reported. The purpose of this study is to evaluate CT findings of intrathoracic neoplasm associated with HOA, and to infer possible mechanism.Meterials and Methods: Seven cases of intrathoracic neoplasm associated with HOA were included In our study. Diagnoses of HOA were made by Tc99m bone scintigraphy or plain radiography. The findings of chest CT scans were reviewed retrospectively, with main interests on their size, location and Internal characteristics, ect.Results: Seven cases of intrathoracic neoplasm consisted of five bronchogenic carcinomas and two thymic tumors. The size of intrathoracic tumors were relatively large ranging from 6cm to 13cm(average 8.0cm). All thoracic neoplasma showed wide pleural contact, and one of them invaded thoracic wall. The range of length of pleural contact was 5-18cm(average 9.9cm). All of seven patients had internal necrosis, and one of them showed cavitation in thoracic mass..Conclusion : Intrathoracic neoplasms associated with HOA had a tendency to be large, to contain internal necrosis, and to widely abut the thoracic pleura.