Aims: Tobacco smoking is among the leading risk factors for chronic disease and early death in developed countries, including Denmark, where smoking causes 14% of the disease burden. In Denmark, many public health interventions, including smoking prevention, are undertaken by the municipalities, but models to estimate potential health effects of local interventions are lacking. The aim of the current study was to model the effects of decreased smoking prevalence in Copenhagen, Denmark. Methods: The DYNAMO-HIA model was applied to the population of Copenhagen, by using health survey data and data from Danish population registers. We modelled the effects of four intervention scenarios aimed at different target groups, compared to a reference scenario. The potential effects of each scenario were modelled until 2040. Results: A combined scenario affecting both initiation rates among youth, and cessation and re-initiation rates among adults, which reduced the smoking prevalence to 4% by 2025, would have large beneficial effects on incidence and prevalence of smoking-related diseases and mortality. Health benefits could also be obtained through interventions targeting only cessation or re-initiation rates, whereas an intervention targeting only initiation among youth had marginal effects on morbidity and mortality within the modelled time frame. Conclusions: By modifying the DYNAMO-HIA model, we were able to estimate the potential health effects of four interventions to reduce smoking prevalence in the population of Copenhagen. The effect of the interventions on future public health depended on population subgroup(s) targeted, duration of implementation and intervention reach.