Presents a review of the scientific literature on cannabis policy and its consequences. The political debate on cannabis policy is often more based on opinions than on evidence. However, evidence-based knowledge is required to design effective cannabis policy. Method. A review of the scientific literature on cannabis policy and its consequences was conducted, focusing on three issues: (1) the difference between formal policy and actual implementation; (2) the effect of policy on prevalence of cannabis use; and (3) the consequences of cannabis policy for users and society. Results. (1) Local authorities, police departments and regional courts differ in how they implement cannabis policy, and implementation typically deviates considerably from the formal policy; (2) The limited available evidence favors the hypothesis that policy and prevalence of cannabis use are not strongly connected. However, there is hardly any literature focusing on the consequences of cannabis policy as implemented; (3) Although in-depth studies are scarce, cannabis policy seems to have negative side-effects for cannabis arrestees well beyond the direct consequences of their arrest. They have, for example, mor