The association between the use of cannabis and the risk of lung cancer is unclear. A hospital-based case-control study was conducted among men in Tunisia and included 149 incident lung cancer cases and 188 controls. Tobacco smoking was significantly associated with an increased risk of lung cancer with odds ratios increasing linearly (p for trend < 0.0001) from 3.9 (95% confidence interval [CI], 1.4-10.9) for former smokers to 17.1 (95% CI: 6.3-46.3) among current smokers who had smoked for >35 years. The odds ratio for the past use of cannabis and lung cancer was 4.1 (95% CI: 1.9-9.0) after adjustment for age, tobacco use, and occupational exposures. No clear dose-response relationship was observed between the risk of lung cancer and the intensity or duration of cannabis use. This study suggests that smoking cannabis may be a risk factor for lung cancer.