Over the past two decades, the Lower Mekong Basin has been developing rapidly, bringing a boom in hydropower developments in this region. There has been heated debate over the trade-offs between the economic benefits from hydropower generation and potentially irreversible negative impacts on its ecosystems and livelihoods of the rural poor. This research aims to examine the social impacts and livelihood vulnerability associated with hydropower development in the Lower Mekong Basin. This talk presents evidence from a large-scale household survey conducted in Lower Sesan II Dam affected villages, Stung Treng, Cambodia. Results from a comprehensive questionnaire will be given to reveal public concerns, livelihood impacts, adaption strategies and associated costs.