Pré-publication, Document de travail: Many public policies, and especially health policies, are aimed at modifying individual behavior. This is particularly true of anti smoking policies. However, health behavior is highly heterogeneous, and so are individual responses to public policies such as taxes or restriction on use. We investigate the effect of a workplace smoking ban which took place in France in 2007. By its national aspect, the French reform offers a good case to study the effect of workplace smoking bans. Using original data on patients who consult tobacco cessation services, we show that the ban caused an increase in the demand for such services, and in the number of successful attempts to quit smoking. However, using survey data, we show that the ban had no measurable effect on overall prevalence in the general population. Models of quasi rational smoking behavior may offer an explanation for these two apparently contradictory findings.