Climate models predict increased drought conditions for the Mediterrean region, putting ecosystems under increasing risk of dieback from direct or indirect effects of droughts. While increasing CO2 has been shown to compensate to some degree the negative impacts of more intense droughts on plant net primary production (NPP), the effect on net ecosystem exchange of carbon (NEP) has not been assessed on Mediterranean forests.Furthermore, large areas of Mediterranean forests result from recent recolonization after land abandonment. Since the carbon sink capacity usually decreases as a forest matures, it is expected that the capacity of unmanaged Mediterranean forests to store carbon will decrease in the coming century. We conducted a simulation study to explore the dynamics of forest NPP and NEP over the 2000-2100 period. We used the NOTG model (Simioni et al. 2016), which is individual-based, process-orientated, and spatially explitcit. We applied the model to the Font-Blanche ICOS experimental site, a typical mixed Mediterranean forest dominated by Aleppo pines and holm oaks. Simulations under 3 climate scenarios (current, moderate change, severe change) suggest that NPP will be enhanced by climate change, both due to higher CO2 and longer growing seasons. The model suggests also that NEP will only be temporarilly enhanced by climate change. The largest effect, however, was a decrease of NEP over time for all scenarios, due to forest maturing, with heterotrophic respiration progressively catching up with NPP. This implies that, regardless of climate change, the sink capacity of large forest areas in southern Europe could strongly diminish during the 21st century.