The goal of this paper is to explain interest groups access to the transparency and access to information policy debate in Spain at the national and subnational level for the last decade. Interest organizations play a key role as agents of policy change. They act as policy entrepreneurs developing data, and information about the importance of transparency policies to guarantee the right to information, to fight against corruption, to enhance citizen’s trust in political institutions, and/or to promote a new way to understand the functioning of democracy. Each organization focuses on several dimensions of this debate, and mobilizes accordingly, trying to have an impact on regulation. Following the persuasion logic, we argue interest groups capacity to have an impact on regulation depends not only in the quality of information they provide, or their level of professionalization, but specially their capacity to reinforce political parties policy positions towards this issue. To develop this argument we have identified all interest organizations that have been active in the governmental, parliamentary and media arenas in Spain and the 17 CCAA for the last decade. The features of each organization is provided by the databases developed by Q-Dem about interest groups.