This article presents survey results on Swedish and Finnish parliamentarians' perceptions concerning their influence over domestic decision making in European Union (EU) matters. In the literature the parliaments in Sweden and Finland are classified as powerful ones that can exert considerable influence over domestic EU policy making. Moreover, Finland and Sweden joined the EU at the same time. Therefore the overall expectation is that the parliaments should be equally powerful. However, the results from this survey indicate a significant difference in perceived influence between the two parliaments. It is obvious that Swedish parliamentarians perceive themselves as more marginalised in relation to the government than Finnish parliamentarians. After trying different explanations, it is concluded that the differences can be ascribed to the parliaments' different organisational set-ups for government oversight.