INTRODUCTION: Cigarette smoking is a serious threat against public health and the most important preventable cause of death. The purpose of this study is to predict the effect on smoking-attributable mortality in Denmark by reducing the number of cigarette smokers. MATERIALS AND METHODS: The simulation model "Prevent" is used. This model operates with the population size and death rates in 1993, data on cigarette smoking from 1973 to 1992 and relative risks for the association between cigarette smoking and lung cancer, chronic bronchitis and emphysema, ischaemic heart disease and stroke. The influence of reduced cigarette smoking on mortality due to these diseases is studied. The expected effect on a smoke-free year group is estimated and so is the effect of the implementation of targets in the Danish Government's Public Health Programme 1999-2008. RESULTS: For the smoke-free year group death rates of ischaemic heart disease are reduced by one third for men and one half for women compared to unchanged cigarette smoking. Death rates of lung cancer, chronic bronchitis and emphysema would be approx. five times lower. If the proportion of Danish cigarette smokers could be reduced by one third over a period of ten years the reduced mortality due to lung cancer, chronic bronchitis and emphysema, ischaemic heart disease and stroke would increase the population (five mio. individuals) by 25,000 after 20 years. DISCUSSION: Intervention against cigarette smoking, especially among young people, would massively reduce mortality from several diseases in the long term. Also in the short term mortality would be reduced substantially by reducing the number of cigarette smokers.