This document outlines the research proposal for a PhD study on pro-poor payment for environmental services (PES) in Vietnam. The study aims to evaluate how the poor have been targeted in current PES policies and projects, identify opportunities and constraints for involving the poor, and recommend conditions for effective pro-poor PES policy. It will use qualitative methods including case studies and participatory approaches at 4 learning sites and 1 action site. The research is important for improving understanding of how PES can impact poverty reduction globally and nationally in Vietnam.