Most forested areas in South East Asia are located in mountainous areas, where they are reservoirs of biodiversity and have important watershed regulating functions. However, the continuing provision of these environmental services may be jeopardized by land use changes. To re-establish natural or productive forests, programs are being proposed in which participating farmers can set aside some of their cultivated sloping land and receive payment for maintaining the newly forested land. This paper compares two types of payments for ecosystems services (or PES)-type programs designed to favor reforestation by farming households: "Payments for forests" (PFF) and "Terraces for forests" (TFF). Both programs involve setting aside sloping land for reforestation but differ in the type and amount of compensation offered. PFF offers annual payments per area of retired land. TFF offers to cover the cost of converting a certain amount of a farm's sloping land into terraces, combined with annual payments per unit area of retired land. The main objective of the paper is to compare the two types of programs in terms of cost-efficiency - can we get the same amount of forest at lower cost? - and equity - will the poorest farmers participate? Using mathematical programming, we developed a set of farm models corresponding to typical farms in a mountainous district in Northern Vietnam. We simulated participation rates of different types of farms in the two types of PES programs. For each PES, we assessed the amount of land converted into forest, the cost of the program, and its impacts on land use and household revenues, at individual farm and village level. Results of our simulations showed that increasing access to irrigated terraces as a way of compensating for converting land to forest increased the participation of the poorest farmers and was more cost efficient than pure cash payments. This suggests that existing PFF programs are biased against the smallest landholders in the reg