BACKGROUND: We determined the predictive power of tobacco smoking on aortic aneurysm as opposed to other risk factors in the general population. METHODS: We recorded tobacco smoking and other risk factors at baseline, and assessed hospitalization and death from aortic aneurysm in 15,072 individuals from the Copenhagen City Heart Study followed for up to 34years and in 56,211 individuals from the Copenhagen General Population Study followed for up to 7years. RESULTS: During follow-up, 335 and 169 individuals developed aortic aneurysm outcomes in the Copenhagen City Heart Study and Copenhagen General Population Study, respectively. According to the magnitude of the hazard ratios, tobacco consumption was the most important risk factor for hospitalization and death from aortic aneurysm, followed by male sex and hypertension in both cohorts. The population attributable risk of aortic aneurysm outcomes due to tobacco consumption was 64% and 47% in the Copenhagen City Heart Study and Copenhagen General Population Study, respectively, and ranked highest among population attributable risks of aortic aneurysm in both cohorts. The absolute 10-year risk for hospitalization or death from aortic aneurysm in males and females consuming above 20g tobacco daily was 3.5% and 1.3%, among those >60years with plasma cholesterol >5mmol/L and a systolic blood pressure >140mmHg. CONCLUSIONS: Tobacco smoking is the most important predictor of future aortic aneurysm outcomes in the general population, with population attributable risks at or above 47%.