Among cancers, lung cancer has the second highest incidence rate and the highest mortality rate in the world. Identifying suitable biomarkers to assist in the prognostic prediction of lung cancer is crucial for developing individualized treatment plans. The hemoglobin, albumin, lymphocyte, and platelet (HALP) score has been applied to predict patient prognosis across a variety of cancers. This study aimed to investigate the predictive value of the HALP score for the prognosis of patients with stage III squamous cell lung cancer.The clinical data of patients with stage III squamous lung cancer who had undergone radical radiotherapy at the Department of Radiotherapy of The Fourth Hospital of Hebei Medical University from January 2011 to December 2020 were retrospectively analyzed. The optimal cutoff values for continuous variables were determined using X-Tile software. A Cox proportional hazards model was used for univariate and multivariate analysis, the Kaplan-Meier method was used for survival analysis, and log-rank test was used to check for differences.A total of 206 patients were included in this study, and the cutoff value for the HALP score was 24.3. There were statistically significant differences between the high- and low-HALP-score groups in terms of alcohol consumption history, tumor-node-metastasis (TNM) stage, prognostic nutritional index (PNI) score, and systemic immune-inflammation index (SII) score. The median overall survival (OS) was 11.0 and 22.0 months in the low- and high-HALP-score groups, respectively (P<0.001), and the median progression-free survival (PFS) was 8.0 and 13.0 months, respectively (P=0.002). Univariate analysis showed that a low HALP score was significantly associated with OS [hazard ratio (HR) =1.698, 95% confidence interval (CI): 1.261-2.286; P<0.001] and PFS (HR =1.584, 95% CI: 1.176-2.132; P=0.002) in patients with stage III lung squamous carcinoma, while the multivariate analysis showed that a low HALP score was the most important factor in OS (HR =1.538, 95% CI: 1.137-2.079; P=0.005) and PFS (HR =1.399, 95% CI: 1.033-1.895; P=0.03) as independent predictors of poor prognosis.In patients with stage III squamous cell lung cancer treated with radical radiotherapy, low baseline HALP score is associated with its poorer OS and PFS and may thus be valuable prognostic factor.2024 AME Publishing Company. All rights reserved.