European integration has prompted a large number of societal and economic interest organizations to promote their cases before the European Union (EU) institutions. These organizations transport socio-economic interests onto the EU level, are sources of information to the EU institutions, exert influence on the EU policy-process, cooperate in the implementation of EU policies and deliver their members’ compliance with European decisions, to name only a few of their important functions. The EU institutions have long recognized the relevance of interest groups. They have accorded to the cross-sectoral European employer associations and trade unions the status of social partners in the social dialogue. In other policy areas, they have established expert committees in which interest organizations routinely represent their members and domains. The Lisbon treaty further strengthens the role of interest groups and civil society in EU decisionmaking by introducing provisions for a participatory democracy at EU level.