OBJECTIVES Worldwide, the association of passive smoking with development of lung cancer has been ascertained. However, it remains unknown of the magnitude of the association in the Chinese population. We thus systematically reviewed the published studies worldwide. METHODS We searched Medline, EMBASE, and three other Chinese databases from their inception to June 30, 2008. We included case-control and cohort studies that investigated the association of passive smoking with lung cancer, and that provided data on the magnitude of the association. Two reviewers screened the eligibility, assessed the extent of the bias, and extracted data independently. We obtained the unadjusted and adjusted estimates of studies. We pooled the trial data using the random-effect model and explored the heterogeneity by the pre-specified variables. RESULTS We included 20 studies (n= 88,379). One was cohort study (n=72829) and 19 case-control studies (cumulative cases: 5 977, and controls: 9 573). Passive smoking increase the risk of lung cancer by 25% (OR=1.25, 95%CI=1.03 to 1.47). Pooling of adjusted estimates of 10 case-control studies (2704 cases and 3495controls) showed that the risk of lung cancer increased by 95% (1.95, 1.49 to 2.55). In female life-long non-smokers, the passive smoking increased the risk of lung cancer by 77% (1.77, 1.22 to 2.58, n=5685), and increased the risk of squamous cell carcinoma and adenocarcinoma of female non-smokers by 99% (1.99, 1.19 to 3.33) and 7% (1.05, 0.45 to 2.51). Because of the limited data, no significant dose-response relationship was found between the risk of lung cancer and the exposure amounts, durations and the initiating age. CONCLUSIONS The increased risk of lung cancer associated with passive smoking in the Chinese population has been ascertained. Passive smoking has a strong association with squamous cell carcinoma.