Prevention appears to be ‘an idea whose time has come’, but the idea is vague. Prevention is a broad concept that represents many ways to define problems and seek to solve them, while preventive policymaking often seems to involve the complete reform of government. Indeed, it is such a wide-ranging idea that it can cover the entirety of social policy and policymaking. Yet, policy studies demonstrate that the scope for major policy change is limited to a small number of areas. Further, many governance reform agendas have come and gone without making an impact. It is far more difficult to identify that the ‘time has come’ for specific policy solutions. Instead, we would expect few problems to receive sufficient attention to prompt major change, and to conclude that policy is as much about the changes that governments don’t make. We use ‘multiple streams analysis’ to demonstrate this difference between heightened attention to a vague idea versus the selection of specific policy solutions and policymaking reforms. We identify two very different categories of ‘window of opportunity’. The first is a single opportunity to select a vague solution to a confusing problem. The second is a series of opportunities to select more specific policy instruments with reference to specific people and problems. We use Social Construction and Policy Design to show how policymakers combine emotion and evidence to make those choices and sell them with reference to ‘target populations’.