The World Health Organization's (WHO) 2002 Annual Report estimated that about 14% of the burden of disease in wealthier countries is attributable to smoking. Smoking related diseases include cardiovascular diseases, cancer and respiratory diseases. This paper presents an estimate of the burden of disease attributable to smoking in Portugal. The estimates are based on the Portuguese demographic and health statistics available for 2005. The most important conclusion of the analysis is that 11.7% of deaths in Portugal are attributable to smoking. If we use disability adjusted life years (DALYs) to measure the burden of disease, we find that 11.2% of death DALYs in Portugal is attributable to smoking. The gender distribution of this amount is very unequal; 15.4% of the male burden of disease and 17.7% of all male deaths can be attributed to smoking, but only 4.9% of the female burden of disease and 5.2% of all female deaths. These estimates are higher than death estimates previously available (Peto et al. 2006); 14% in men and only 0.9% in women. This paper also presents estimates of the burden of reducible disease, that is, the reduction in mortality and DALYs that would occur if all current smokers quit and thus experienced the mean risk of ex-smokers, which is lower than for current smokers but typically not as low as for never-smokers. Our estimates are that the burden of disease would decrease by 5.8% (7.8% in men and 2.8% in women), and that deaths would decrease by 5.8% as well (with an 8.5% and 2.9% decrease in men and women, respectively). The paper also includes estimates of the burden of disease generated by smoking related disability. Smoking related illnesses generated 121,643 DALYs, 72,126 (59%) of which are attributable to smoking and 12,417 would be reducible if all smokers were to quit.