Abstract: Objective To investigate the influencing factors associated with pulmonary infection during CHOP regimen (cyclophosphamide + doxorubicin + vincristine + prednisone) treatment in patients with non-Hodgkin lymphoma (NHL). Methods A retrospective analysis was conducted on the clinical data of 90 patients with non-Hodgkin lymphoma (NHL) admitted to Qidong People's Hospital from January 2022 to January 2025. All patients received the CHOP regimen chemotherapy. Based on the infection status, the patients were divided into the pulmonary infection group (n = 28), non-pulmonary infection group (n = 15), and no-infection group (n = 47). According to the severity of infection, the pulmonary infection group was subdivided into the mild-to-moderate infection group (n = 13) and the severe infection group (n = 15). The baseline characteristics of patients were collected. The systemic immuneinflammation index (SII), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and prognostic nutritional index (PNI) were compared among groups. Univariate and multivariate logistic regression analyses were performed to identify factors influencing pulmonary infection in NHL patients. Results After chemotherapy, SII, NLR, and PLR levels were significantly lower than before chemotherapy, while PNI was significantly higher than before chemotherapy (P＜0.05). There were significant differences in the proportion of smokers, lymphocyte count, and forced expiratory volume in one second (FEV₁) before chemotherapy among groups (P＜0.05). No significant difference was found in PNI among groups (P＞0.05). However, there were significant differences in SII, NLR, and PLR (P＜0.05). Furthermore, no significant difference was found in NLR and PNI between the two subgroups (P＞0.05). The SII and PLR were significantly lower in the mild to moderate infection group than in the severe infection group (P＜0.05). The results of multivariate logistic regression analysis showed that high FEV₁ before chemotherapy was an independent protective factor for reducing the risk of pulmonary infections in NHL patients (P＜0.05). Conclusion During CHOP regimen treatment for NHL, a higher prechemotherapy FEV₁ is an independent protective factor against pulmonary infections, while smoking history, lymphocyte count, and inflammatory indices also hold certain predictive value.