How do interest group organisations use social media in a lobbying campaign? This paper provides descriptive analyses of the use of Twitter by 50 organisations active in the lobbying of transparency laws in Spain in the last decade. The high levels of consensus on the need for transparency regulation provide an ideal case for expanding on the emerging literature on interest groups and social media. We use contents analysis in order to describe how organisations focus on multiple issue dimensions using quantitative contents analysis of Twitter conversations mentioning the term transparencia and relevant policy actors. We also look into structural analysis in order to shed light on the nature of interactions between the lobbying organisations, as well as their interactions with policy makers and the general public. Our analyses show varying lobbying strategies that can be explained by social media traces of policy process, thus advancing the knowledge on interest group behaviour.