<i>Objective:</i> The aims of this study were to identify prognostic factors for overall survival (OS) in patients with small cell lung cancer (SCLC) and to construct a prognostic index on the basis of their expected OS. Long-term survivors were also given special attention. <i>Methods:</i> We retrospectively analyzed 295 patients diagnosed with SCLC from January 2002 to September 2007 at the Severance Hospital, Seoul, Republic of Korea. Patient history was reviewed regarding both clinical and tumor-related markers, and treatment-related factors were also evaluated. <i>Results:</i> There were 131 (44.4%) patients with limited disease (LD) and 164 (55.6%) with extensive disease (ED). Median follow-up lasted 9.4 months. Objective response to chemotherapy was 66.8%. The median survival time (MST) was 11.2 months in all patients, 20.4 months in LD patients, and 7.7 months in ED patients. The median progression-free survival was 9.4 months. Independent prognostic factors for overall survival (OS) were extent of disease, performance status, and CYFRA 21-1 level. We classified all patients into four groups based on the results of multivariate analysis using classification and regression tree analysis. Median survival times were 22.7, 13.7, 8.5, and 3.2 months, respectively. A total of 51 (17.3%) patients from the entire study population were evaluated for long-term survival, which was defined as survival >2 years. Their MST was 43.1 months, and extent of disease, performance status, and CYFRA 21-1 were independent prognostic factors for long-term survival. <i>Conclusions:</i> We confirmed the well-known prognosticators, disease extent and performance status, in our patients, but further identified CYFRA 21-1 as independent prognostic factor. A prognostic index was constructed to create four classifications of SCLC considering these variables.