BACKGROUND The hemoglobin, albumin, lymphocyte, and platelet (HALP) score is a prognostic factor in patients who have some types of malignant tumors. The aim of this study was to investigate the prognostic significance of the HALP score in patients with small cell lung cancer (SCLC) before first-line treatment with etoposide. MATERIAL AND METHODS A retrospective study included 178 patients with SCLC who received first-line chemotherapy with etoposide between September 2015 and May 2019. The baseline clinical characteristics and blood parameters were recorded. Univariate and multivariate analysis and Kaplan-Meier plots were used to identify the factors associated with progression-free survival (PFS). RESULTS The optimal cut-off values of the HALP score was determined by X-tile software to be 25.8. Univariate and multivariate analysis showed that in 178 patients, the HALP score, body mass index (BMI), and serum albumin levels had no prognostic significance. In the patient age group <65 years, a BMI ≥24 kg/m² was an independent prognostic factor (HR, 1.943; 95% CI, 1.251-3.018) (P=0.003). In the patient age group ≥65 years, a HALP score >25.8 was an independent positive prognostic factor for outcome following first-line treatment with etoposide (HR, 0.483; 95% CI, 0.270-0.865) (P=0.014). CONCLUSIONS In patients <65 years with SCLC who underwent first-line treatment with etoposide, a BMI ≥24 kg/m² an independent prognostic factor, and in patients ≥65 years, a HALP score >25.8 was an independent predictor of improved outcome, associated with increased PFS.