The essay deals with the effects and the implications of the presence of mafia on the local economic development. The analysis has been carried out with reference to the theoretical perspective on the social capital. The amount of social capital mafia can dispose of is a fundamental element in order to control the territory: the mechanism of extortion-protection heavily affects the social relationships and the economic activities that take place in it. The thesis is that a high presence of social capital belonging to mafia is a serious hindrance to the self-sustained development of some areas of Southern Italy. Wherever these are more deeply embedded, mafia organizations discourage the productive investments and create negative or vitiated effects on the entrepreneurship, through the distortion of the regulations guiding the market, the use of violence and of illegally stored capitals.