After birth, children must remain protected against smoking, for example using smoke-free zones. We showed that a smoke-free zone surrounding the Erasmus MC and two schools was highly supported by adults (76%) and paediatric patients (89%) and that the number of smokers in the zone almost halved following its implementation. The increase of smokers outside the border was much smaller than the decrease inside the border, showing that a smoke-free zone demotivates smoking. Pointing out the smoke-free policy to smokers inside the zone often elicited a positive or neutral response (64%) and lead to smokers leaving the zone or extinguishing their cigarettes (74%).