Background: Selecting carboplatin or cisplatin in the treatment of poor prognosis and/or extensive stage SCLC remains controversial. We performed an IPD meta-analysis from published randomized trials. Methods: In June 2009, a systematic review was performed to identify randomized phase III trials comparing cisplatin- vs. carboplatin-based CT in the first-line treatment of SCLC. Primary endpoint of the meta-analysis was overall survival (OS). IPD (baseline characteristics, treatment details, toxicity and outcome measures) were obtained via collaborating with all groups identified by the systematic review. All statistical analyses were stratified by trials. OS and progression-free survival (PFS) curves were compared using the log-rank test. Response rate was compared using the Mantel-Haenszel test. Results: All four eligible trials were included in the analysis with a total of 663 patients (329 cisplatin, 334 carboplatin). Baseline characteristics were well balanced between arms. Median age was 67 years (27-86). Performance status (PS) was 0-1 in 72%, 2-3 in 28%; 68% of patients had extensive stage. With 589 deaths recorded (89%), median OS was 9.5 months with cisplatin, and 9.5 months with carboplatin (hazard ratio [HR] carboplatin vs. cisplatin 1.03, 95% confidence interval [CI] 0.88–1.22; p = 0.69). There was no evidence of treatment difference between cisplatin and carboplatin according to different gender, stage, PS or age. Response rate was 67.5% and 65.6%, with cisplatin and carboplatin, respectively (relative risk 0.96, 95% CI 0.82-1.13; p = 0.66). Median PFS was 5.3 and 5.5 months, for cisplatin and carboplatin, respectively (HR 1.01, 95% CI 0.86–1.19; p = 0.90). Toxicity profile was significantly different: hematological toxicity was higher with carboplatin, and non-hematologic toxicity higher with cisplatin. Conclusions: COCIS is the first IPD meta-analysis in the treatment of poor prognosis and/or extensive stage SCLC. We found no survival difference between cisplatin- and carboplatin-based CT but a different toxicity profile was reported.