Background: Chemotherapy (CT) in combination with thoracic radiotherapy (RT) can improve the survival of patients with limited-stage small cell lung cancer (LS-SCLC). In the current study, we evaluated the prognostic factors, especially the effect of the therapy integration and the timing of RT, on survival. Patients and Methods: We retrospectively studied 142 patients with LS-SCLC. All patients received thoracic RT and 126 patients received at least 2 cycles of CT; 38 patients received RT following CT cycles, 32 received RT between CT cycles, and 56 received RT concurrently with CT. Results: For all patients, the 1-, 3-, and 4-year overall survival (OS) rates were 68.3, 31.2, and 28.6%, respectively. In univariate analyses, the volume of the primary tumor, T classification, CT, the target volume, the RT dose, and the treatment response were significantly associated with OS. The multivariate analysis showed that CT, the timing of RI, and RT dose were independent factors influencing the OS. Conclusion: Concurrent chemoradiotherapy could result in high survival rates, and early integration of thoracic RT was associated with a better outcome. A radiation dose-response relationship was observed in our study.