The recognition of the serious health-damaging effects of tobacco smoke exposure has initiated several preventive programmes on the national and international levels worldwide. In the last decade, a considerable decrease in the prevalence of active smoking was observed in Denmark, changing the country from a poor to a favourable position in comparison to other EU countries. However, second-hand tobacco smoke exposure, especially in homes, still ranks Denmark among the problematic countries in Europe. This poorly recognised and studied discrepancy calls for further research and effective targeted interventions on population level.