Contributions by non-governmental organizations (NGOs) to European governance supposedly enhance participatory democracy. It matters for this democratic surplus how NGOs foster relationships to both policy-makers and publics by engaging in inside and outside lobbying on European Union policies. This article investigates the factors that explain this lobbying behaviour. It contrasts organization-level hypotheses on the NGOs’ relational and resource characteristics with issue-level hypotheses on the complexity, salience and beneficiary group of the policy issue. Expectations are formulated under the assumption that different logics of influence and reputation drive inside and outside lobbying by NGOs. The findings suggest that issue-level characteristics have more explanatory power than organization-level factors. More salient, less complex issues and issues involving a public good have significantly higher odds of outside lobbying, while public goods attract less inside lobbying. The logic of reputation seems to capture outside lobbying, while the logic driving inside lobbying remains more puzzling.