Idiopathic pulmonary fibrosis (IPF) is a debilitating condition, with a life expectancy of 2 to 5 years after diagnosis. Pirfenidone is a drug that has been shown to reduce the decline in forced vital capacity (FVC). We sought to identify whether different patterns on high-resolution computed tomography (HRCT) have different clinical effects through a retrospective comparison of baseline values and changes in pulmonary function tests (PFTs) after treatment with pirfenidone. We retrospectively analyzed data from IPF patients treated with pirfenidone at Nanjing Drum Tower Hospital in Jiangsu Province, China. According to the HRCT pattern, the patients were divided into usual interstitial pneumonitis (UIP) and possible UIP groups. Baseline clinical characteristics and changes every 6 months in the PFTs during the follow-up period were compared between the 2 groups. A total of 65 consecutive patients were enrolled. According to the HRCT pattern, patients were clustered into the UIP group (n = 46) and possible UIP group (n = 19). No difference was observed in the baseline PFTs ratio between the 2 groups. The FVC values of the 2 groups were not significantly different at the initial treatment and at 6 and 12 months after pirfenidone treatment (P= .081, 0.099, and 0.236, respectively). The improvement in % diffusion capacity of the lung for carbon monoxide (%DLCO) was higher in the possible UIP group after 6 and 12 months of pirfenidone treatment (P= .149, 0.026, and 0.025, respectively). The annual decrease in FVC was not significantly different between the 2 groups, and the annual decrease in %DLCO in the UIP group was significantly higher than that in patients with the possible UIP type (−7.767 ± 12.797 vs 0.342 ± 20.358,P< .05). These results indicate that patients with IPF with a possible UIP pattern on HRCT showed indications of a good response to pirfenidone.