The aim of the study was to evaluate the carbon storage capability of an unmanaged old-growth deciduous forest developing inside a Natural Reserve. Our research aims to emphasize how the conservative management, by determining the actual structure and species composition, resulted in a high carbon storage capability. The results highlight that the forest stores a large carbon amount (C_Tot = 418 Mg C ha^-1) with the greater pool in the aboveground biomass and in the soil (42%). In particular, among the most abundant species, Populus spp. and Quercus robur are the major carbon sink of the forest, accounting for 31% and 63% of the forest aboveground biomass. In addition, the total economic benefits from carbon storage of the forest of 11 209 $ ha^-1 was estimated. Thus, preserving this type of forest structure and tree species composition can ensure in the future the same forest contribution to the local carbon stock.