Objective: To investigate the pulmonary CT findings in antineutrophil cytoplasmic antibodies (ANCA) associated small vessel vasculitis(AASV). Methods: Clinical features of 25 patients with AASV hospitalized from January 2012 to December 2016 were randomly selected, and their pulmonary CT scans were analyzed retrospectively. Results: Of all the 25 AASV patients, 11 cases were male and 14 cases were female. The mean age of the subjects was 62 years old. These cases were divided into two groups: a cytoplasm antineutrophil cytoplasmic antibodies (c-ANCA) positive group (n=5) and a peripheral antineutrophil cytoplasmic antibodies (p-ANCA) positive group (n=20) in their peripheral serum. The pulmonary CT images were as follows: interstitial pneumonitis (n=19); patchy ground glass shadow (n=10); nodule and mass (n=7); pleural thickening (n=5); emphysema and bullae (n=4); bronchiectasis (n=4); air bronchogram (n=3); cavity (n=3); pleural effusion (n=3); honeycomb lung (n=1); enlarged mediastinal lymph nodes (n=1). In the three main CT images, the proportion of interstitial pneumonitis were significantly higher in patients with p-ANCA positive than that in the c-ANCA positive cases (P<0.05). There was no significant difference in patchy ground glass shadow, the nodule and mass involvements between two groups (P>0.05). Conclusion: The pulmonary CT imaging in AASV shows variety, mainly including interstitial pneumonitis, patchy ground glass shadow, and nodule and mass. The pulmonary CT scans in patients with p-ANCA positive are easy to show interstitial pneumonitis.