Thus, the relative risk is much higher for lung cancer than for CHD, and the attributable risk expressed as a proportion is also much higher for lung cancer. However, if an effective smoking cessation program were available today and smoking were eliminated, would the preventive impact be greater on mortality from lung cancer or from CHD? If we examine the table we see that if smoking were eliminated, 256 deaths per 100,000 from CHD would be prevented in contrast to only 130 from lung cancer, despite the fact that the relative risk is higher for lung cancer and despite the fact that the proportion of deaths attributable to smoking is greater for lung cancer. Why is this so? This is a result of the fact that the mortality level in smokers is much higher for CHD than for lung cancer (669 compared to 140) and that the attributable risk (the difference between total risk in smokers and background risk) is much greater for CHD than for lung cancer.