PURPOSE: Pretreatment systemic inflammatory response has been confirmed to have prognostic value in patients with inoperable non-small-cell lung cancer (NSCLC). Increasing studies show that the modified Glasgow prognostic score (mGPS), a prognostic score based on C-reactive protein (CRP) and albumin, is a prognostic factor in these patients. This study was aimed at recognizing possible prognostic factors and new prognostic scores of inoperable NSCLC based on pretreatment systemic inflammatory response. PATIENTS AND METHODS: We retrospectively reviewed the clinicopathological data of 105 patients with inoperable NSCLC who received first-line chemotherapy as initial treatment. Univariate and multivariate analyses of progression-free survival (PFS) and overall survival (OS) for prognostic factors and scores were performed. RESULTS: The serum CRP, lactate dehydrogenase (LDH), cancer antigen 125 (CA125), and pathological type were independent pretreatment prognostic factors for PFS and OS. A new score was assembled by CRP, LDH, and CA125. In multivariate analysis, when the mGPS and the new score were covariates, only the new score retained independent prognostic value for both PFS (P<0.001; hazard ratio =2.12; 95% confidence interval: 1.60-2.82) and OS (P<0.001; hazard ratio =1.82; 95% confidence interval: 1.33-2.48). CONCLUSION: The new score based on pretreatment serum level of CRP, LDH, and CA125, indicates the prognosis of both PFS and OS in patients with inoperable NSCLC who were treated with first-line systemic chemotherapy, and it was found to be more effective than mGPS.