Protection from natural hazards is the most important function of mountain forests from an ecological, economic and social point of view. This assertion has been widely debated in recent years by a number of authors. In this paper we focus on the economic aspects of the protective function of forests, developing a quick and simple estimation method that can be applied on a local scale. We present the results of its application in an Italian Alpine forest. After having identified the main forest attributes directly or indirectly involved in protection, the economic value of the protective function for homogeneous zones was estimated by applying the replacement cost method. This value enables environmental concerns to be included in forest planning and political decision-making.