As European countries move towards steeper cuts in greenhouse gases emissions, questions are mounting, in the forest sector, about the best balance between policies that favor carbon sequestration in biomass, and policies that favor fossil-fuel substitution, with potentially conflicting implications for forest management. We provide insights on this debate by comparing the environmental and economic implications for the French forest sector of a "stock" policy (payment for sequestration in situ), a "substitution" policy (subsidy to fuelwood consumption), and a combination thereof - all calibrated on the same price of carbon. To do so, we use the French Forest Sector Model (FFSM), which combines a dynamic model of French timber resource and a dynamic partial-equilibrium model of the French forest sector. Simulations over the 2010-2020 period show that the stock policy is the only one that performs better than business-as-usual in terms of carbon. In the substitution policy, cumulative substitution benefits are not sufficient to offset carbon losses in standing forests over this biologically short, but politically relevant period of time. And the combination policy does not perform better. However, the stock policy has negative impacts on consumers welfare, its costs are increasing over time as carbon is accumulated, and it raises political economy questions about the negotiability of the reference against which excess carbon is measured.