AbstractBackgroundCurrent estimates of lifetime costs of smoking are largely based on model analyses using etiologic fractions for a variety of diseases or Markov chain models. Direct estimation studies based on individual data for health costs by smoking status over a lifetime are non-existent.MethodsWe estimated lifetime costs in a societal perspective of 18-year-old daily-smokers (continuing smoking throughout adult life) and never-smokers in Denmark, as well as lifetime public expenditures in the two groups. Main outcomes were lifetime net public expenditures and lifetime health costs according to OECD definitions and lifetime earned incomes. Estimates of these outcomes were based on registries containing individual-level data. Confounder-adjusted differences between daily-smokers and never-smokers were interpreted as smoking-attributable lifetime public expenditures and costs.ResultsThe net lifetime public expenditure is, on average, €20 520 higher for male 18-year-old daily-smokers than for never-smokers, but €9771 lower, for female daily-smokers compared with never-smokers. In male 18-year-old daily-smokers, average lifetime health costs are €9921 higher and average lifetime earned incomes are €91 159 lower than for never-smokers. The corresponding figures are €5849 higher and €23 928 lower, respectively, for women.Conclusion18-year-old male daily-smokers are net public spenders over their lifetime compared with never-smokers, while the opposite applies for women. In Denmark, smoking is associated with higher lifetime health costs for society and losses in earned incomes—both for men and women.