ObjectiveTo investigate the CT features and clinicopathological features of thin-walled cystic lung cancer with the largest diameter less than or equal to 3 cm.MethodsThe CT features and clinicopathological data of 26 thin-walled cystic lung cancer patients diagnosed by chest CT and surgical or puncture pathology were retrospectively analyzed. There were 16 males and 10 females, with an average age of 62 years.ResultsThe lesions were distributed in different pulmonary lobes, all of which were peripheral. The maximum diameter of lesion was 21.4 mm on average, and the maximum diameter of cyst was 12.9 mm on average. Among them, there were 19 patients of lobulation sign, 18 patients of spicule sign, 16 patients of pleural indentation, 9 patients of vascular convergence sign, 7 patients of bronchus sign, 21 patients of irregular inner wall, 26 patients of uneven thickening of cystic wall, 18 patients of intra-cystic separation, and 10 patients of vessels through the cystic cavity. The pathological types were all adenocarcinoma and 24 patients were invasive adenocarcinoma.ConclusionAll patients were peripheral adenocarcinoma. CT not only shows the common typical signs of lung cancer, but also has the characteristic fertures of irregular inner wall, intra-cystic separation and vessels through the cystic cavity.