Programmes for the Disarmament, Demobilisation, and Reintegration (DDR) of ex-combatants are intended to support the peace process in which they are embedded. Yet their outcomes are not always clear. Calls for a more holistic approach with greater local ownership have often been made, but can be difficult to implement. This study of DDR in Sierra Leone and Liberia applies the concept of ‘participation’, which means genuinely involving intended beneficiaries in the process. It is based on semi-structured interviews with a range of stakeholders, and a survey and focus group discussions with ex-combatants. There is little indication of a participatory approach: ex-combatants reported serious problems with information, consultation, and input to decision-making. However, where greater participation is seen, there are statistically significant associations with better outcomes in terms of work, economic status, and community relations. The data illustrate how post-war social capital can be built up—or undermined—by the degree to which reintegration processes were participatory. Participation, social capital, and loss of faith in the process are seen to be significant in the way DDR can contribute to the wider peace process.