The choice between environmental policies is traditionally considered in terms of ex ante versus ex post interventions on the behavior of (potential) injurers that (can) cause an environmental accident with a consequent environmental damage. Moreover, market-based policies can be implemented as an indirect form of incentive for correct behavior. The two market-based policies, taxes and tradable permits system, are compared on the basis of the difference between price and quantity instruments. And finally, the real situation of the presence of an environmental policy mix is considered as a research challenging topic.