AbstractThis paper describes the complex hydrogeological, legal framework and socioeconomic costs of the groundwater protection in major groundwater basins (MGBs) in Poland in accordance with European directives. The hydrogeological criteria developed in Poland for establishing MGBs and the principles of their protection provide more details to the directives that are in force in Europe, which define the general principles for groundwater protection. The procedure of establishing MGB protection zones is connected with a change in local plans and land development and requires an analysis of the cost–benefit relationship in the sphere of social economy in the sector of public economics. The cost assessment was performed on the basis of data from hydrogeological documentations, and the aggregation of subareas to which the same existing and planned development can be attributed. A legal analysis of bans, orders and restrictions together with the identification of the risk of claims in specific hydrogeological and development conditions was a fundamental issue of research. These costs depend on the acreage and land use of the protected area. The unit costs of MGB protection, calculated per 1 km2 of the protection area, for six sample basins were estimated at €120 to €208,000/2 years/1 km2. The highest costs are generated by establishing protection in urban areas, while the lowest costs are generated in forest areas.