INTRODUCTION: In 2003, Europe was affected by widespread droughts affecting over 100 million people, a third of the EU territory, with a cost of at least 80 billion euros. In response, the EU Council of Ministers asked the European Commission to address the challenges of water scarcity and drought. The European Commission in 2007 issued the 'Communication on water scarcity and droughts in the European Union'. The Communication Paper laid down a water hierarchy in which water demand management should come first, and alternative supply options are only considered once the potential for water efficiency has been exhausted. The Communication Paper listed several policy options needed to manage water in a way that addresses water security, including putting a price on water, allocating water-related funding more efficiently, fostering water-efficient technologies and practices, and fostering the emergence of a water-saving culture in Europe. Since the release of the Commission's Communication, droughts in 2011 and 2012 affected large parts of Southern, Western and even Northern Europe, with rainfall as low as 40% of normal levels. By 2030 the number of river basins in Europe affected by water insecurity will increase by 50%. Regarding water use, around 20-40% of Europe's available water resources are being wasted while water consumption in Europe is projected to increase by 16% in 2030. Meanwhile, 60% of European cities are currently over-exploiting their groundwater resources. Traditionally, urban water managers facing increased demand alongside varying levels of supplies have relied on large-scale, supply-side infrastructural projects, such as dams and reservoirs, to meet increased demands for water; however, these projects are environmentally damaging and economically unfeasible. Environmental costs include disruptions of waterways that support aquatic ecosystems, while economic costs stem primarily from a reliance on more distant water supplies often of inferior quality, which not only increases the costs of transportation, but also the cost of treatment; furthermore, with the vast majority of water resources being transboundary supply-side projects can create political tensions due to water crossing intra- and inter-state administrative and political boundaries. Demand management is the process by which improved provisions of existing water supplies are developed. In particular, demand management promotes water conservation during times of both normal and atypical conditions, through changes in practices, culture, and people's attitudes towards water resources. Demand management involves communicating ideas, norms and innovative methods for water conservation across individuals and society; the purpose of demand management is to positively adapt society to reduce water consumption patterns and achieve water security. METHODS: Using data from semi-structured interviews with urban water managers of leading cities in Europe this paper tests the hypothesis that demand management tools are critical in achieving urban water security. RESULTS: The paper finds that in all case studies urban water managers/institutions are the critical drivers of change towards achieving urban water security. This is because institutions can create a vision and then use a variety of demand management tools to modify behaviour to achieve this vision. However, there are significant barriers to achieving behavioural change and water conservation. These barriers are both external (economic, institutional, legal, technological) and internal (psychological and cultural). CONCLUSION: This paper finds that effective demand management can be used as a tool to reduce water consumption and defer economically and environmentally-costly supply-side projects. To achieve this, strong visions along with a portfolio of demand management strategies are required to overcome barriers to water conservation. 1. EUROPEAN COMMISSION. 2002. The Water Framework Directive: Tap into it ! Available: http://ec.europa.eu/environment/water/water-framework/pdf/tapintoit_en.pdf.