Research has shown that industrial firms and organisations engaged in lobbying during the making and revision of the European Union Emissions Trading System (EU ETS). However, little is known on how they went about lobbying. This article provides insight into industrial lobbying during the revision of the EU ETS by focusing on six industrial firms from Sweden and Norway, examining how and where they lobbied, and whether their lobbying was shaped by originating from an EU member state or not. The article finds that EU membership did influence how and where firms lobbied. Compared to Swedish firms, Norwegian firms lobbied less alone, via national associations and national institutions, and this limited Norwegian firms’ ability to lobby at the European level.