Contingent Valuation (CV) is one of the most used methods for environmental resources evaluation, within cost benefit analysis. Here, CV is used to estimate boating demand function of an important wetland in Italy: the Venice lagoon. Demand functions have been utilised to assess the consequences of annual charge for lagoon recreational use by boats. Valuation has been carried out using the classic “bidding game” approach during interviews to a representative sample of boat owners which go on a trip to the lagoon. The representative group has been gained from a preliminary search within the wet docks facing the lagoon and within the moorage holders on the canals in the Venice historic centre.