How, and under which conditions, can consultative committees exert influence if they have access to legislators (voice) but no formal veto power (vote)? In drawing on the Committee of the Regions and the European Economic and Social Committee of the European Union, this book shows that consultative committees face several challenges when it comes to influencing the content of policies, but are nevertheless sometimes successful in getting their opinions heard. It develops a sender-receiver model and puts it to a comprehensive empirical test. A quantitative analysis and three in-depth case studies on the European citizens' initiative, the European grouping of territorial cooperation and the Liberalisation of Community Postal Services show how capacities, incentives and preferences of consultative committees and legislative decision-makers need to be configured to allow for the influence of the CoR and the EESC.