Constructed wetlands (cws) for wastewater treatment may be part of the answer to the urgent need for a change in the approach to wastewater treatment in developing countries. Although thailand has several cws, there have been no studies of their sustainability. To remedy this, the sustainability of three promising cws in very different settings was assessed. These were located at koh phi phi, a world-renowned international tourist and holiday resort; sakon nakhon, a northeastern provincial capital; and ban pru teaw, a small post-tsunami village on the andaman coast. Key stakeholder interviews, questionnaires and household interview surveys, together with existing data and on-site measurements of the key pollutant content of wastewater were used to evaluate the systems.