Purpose: To determine whether hemogram parameters have prognostic effects on survival in patients with extensive-stage small cell lung cancer (ED-SCLC). Methods: This retrospective analysis included 113ED-SCLC patients, who were followed in an oncology clinic. The data regarding the baseline patient demographic characteristics, complete blood count (white blood cell, red blood cell, hemoglobin, hematocrit, mean platelet volume, platelet, total neutrophil, total lymphocyte, total monocyte, neutrophil-to-lymphocyte ratio [NLR], platelet-to-lymphocyte ratio [PLR], and monocyte-to-lymphocyte ratio [MLR]), and survival were analyzed. According to the ROC curve drawn for overall survival (OS) analysis, the cutoff values were determined as follows: NLR >= 3, with 71.4% sensitivity and 63.6% specificity; PLR >= 0.150, with 68.1% sensitivity and 52.4% specificity; and MLR >= 0.367, with 64.4% sensitivity and 71.4% specificity. Results: Of the 113 patients with ED-SCLC, 92 (81.4%) were men and 21 (18.6%) were women. The median age was 65 years (range, 35-81 years). NLR was <3 in 40 (65.4%) patients. Patients with NLR <3 had significantly higher OS than those with NLR >= 3 (15 vs. 5 months, respectively, p < 0.001). Patients with PLR <150 had significantly higher median OS than those with PLR >= 150 (14 vs. 6 months, respectively, p = 0.014). The median OS was significantly greater in patients with MLR <0.367 compared to that in patients with MLR >= 0.367 (11 vs. 6 months, respectively, p = 0.016). In multivariate analysis, NLR was the only factor associated with OS (HR = 2.26, 95% Cl 1.24-4.10). Conclusion: NLR was determined as an independent negative prognostic factor for OS in ED-SCLC patients at diagnosis, thus may help determine disease prognosis as a useful prognostic marker.