BACKGROUND In malignant tumors, inflammation plays a vital role in the development, invasion, and metastasis of cancer cells. Diffuse large B-cell lymphoma (DLBCL), the most common malignant proliferative disease of the lymphatic system, is commonly associated with inflammation. The international prognostic index (IPI), which includes age, lactate dehydrogenase (LDH), number of extranodal lesions, Ann Arbor score, and Eastern Cooperative Oncology Group (ECOG) score, can evaluate the prognosis of DLBCL. However, its use in accurately identifying high-risk patients and guiding treatment is poor. Therefore, it is important to find novel immune markers in predicting the prognosis of DLBCL patients. AIM To determine the association between the systemic immune inflammation index (SII), ratio of lymphocytes to monocytes (LMR), ratio of LMR to LDH (LMR/LDH), and prognosis of patients with DLBCL. METHODS A total of 68 patients diagnosed with DLBCL, treated in our hospital between January 2016 and January 2020, were included. chi(2) test, Pearson's R correlation, Kaplan Meier curves, and Cox proportional risk regression analysis were used. The differences in the SII, LMR, and LMR/LDH among patients with different clinicopathological features were analyzed. The differences in progression-free survival time among patients with different SII, LMR, and LMR/LDH expressions and influencing factors affecting the prognosis of DLBCL patients, were also analyzed. RESULTS The LMR and LMR/LDH in patients with Ann Arbor stage III-IV, ECOG score >= 2, and SII, IPI score 2-5 were significantly higher than those of patients with Ann Arbor stage I-II and ECOG score < 2 (P < 0.05). Patients with high SII, LMR, and LMR/LDH had progression-free survival times of 34 mo (95%CI: 32.52-38.50), 35 mo (95%CI: 33.42-36.58) and 35 mo (95%CI: 33.49-36.51), respectively, which were significantly lower than those with low SII, LMR, and LMR/LDH (P < 0.05); the SII, LMR, and LMR/LDH were positively correlated (P < 0.05). Cox proportional risk regression analysis showed that the SII, LMR, and LMR/LDH were influencing factors for the prognosis of DLBCL patients (hazard ratio = 1.143, 1.665, and 1.704, respectively; P < 0.05). CONCLUSION The SII, LMR, and LMR/LDH are related to the clinicopathological features of DLCBL, and they also influence the prognosis of patients with the disease.