Objective: This study aims to analyze the clinical features and prognosis of checkpoint inhibitor pneumonitis (CIP) in lung cancer patients and to provide reference for clinicians. Methods: Lung cancer patients with CIP treated at the First Affiliated Hospital of Nanjing Medical University from September 2018 to September 2022 were collected and followed up until December 2022. Baseline and clinical characteristics were described, and Survival analysis were conducted to explore the risk factors for death. Results: A total of 75 patients were analyzed, including 71 males and 4 females, with a mean age of 66.7±7.6 years. There were 60.0% of patients with emphysema ? and 36.0% with pre-existing interstitial lung abnormalities (ILA) or interstitial lung disease (ILD). There were 36 cases (48.0%) manifested as organizing pneumonia (OP) pattern on imaging, 28 cases (37.3%) as nonspecific interstitial pneumonia (NSIP) pattern, 6 cases (8.0%) as acute interstitial pneumonia (AIP)/ acute respiratory distress syndrome (ARDS) pattern, and 5 cases (6.7%) as other patterns. Significant differences existed between patients with ILA/ILD and those without, and between patients manifested as AIP/ARDS pattern on imaging and others. Conclusion: For CIP in lung cancer patients, those with pre-existing ILA/ILD have a poorer prognosis than those without, and those manifested as AIP/ARDS pattern on imaging have a poorer prognosis than those manifested as others.