Combined modality therapy is the standard care for limited stage-small cell lung cancer (LS-SCLC) and has led to a significant improvement in patients' survival. This study sought to investigate and define the importance of prognostic effects of known and controversial factors especially the impact of smoking status and treatment strategies. A total of 284 patients with LS-SCLC were diagnosed and prospectively followed from 1997 to 2008 at Mayo Clinic; their characteristics and survival outcome were assessed on the basis of age, gender, smoking history, performance status (PS), tumor recurrence or progression, and treatment using Cox proportional hazards models. Our main results are as follows: (1) Although neither smoking status (former or current smokers) nor intensity (pack-years smoked) at the time of SCLC diagnosis were significant survival predictors, compared to continued smokers (who never quit smoking), patients who quit at or after diagnosis cut the risk of death by 45% (HR=0.55, 95% CI 0.38-0.79); patients who quit before lung cancer diagnosis also experienced survival benefit (HR=0.72, 95% CI 0.52-1.00). (2) Thoracic radiotherapy and platinum-based chemotherapy could significantly improve survival but the timing (within or after one month of diagnosis) of starting chemotherapy or radiation therapy did not. (3) After adjusting for other known factors, a lower PS did not predict poorer survival, suggesting that PS should not be the only factor for making treatment decisions. In conclusion, this study demonstrated the negative impact of continued cigarette smoking on survival; therefore, clinicians and all care providers should strongly encourage smoking cessation at diagnosis of LS-SCLC.