Payment for environmental services (PES) can be a poverty reduction strategy. Findings from two PES case studies in Vietnam indicate that the involvement of the poor is enhanced by increasing attention and interest from donors and the private sector. However, their participation is limited due to political influences which weaken environmental services monitoring, and weak local intermediaries who are limited in their capacity to represent and protect the poor. Whether PES schemes can be pro-poor depends on the scope of the project, the political, social and economic context of the case, and the local definition of poverty. Capacity building for the poor, coupled with better coordination for transparent and equitable benefit-sharing and monitoring mechanisms, need to be in place to ensure that the poor will not be marginalised.