After the Lisbon Treaty, the EU political system has become ever more complex with national parliaments having the possibility to participate actively. This article investigates the conditions under which national parliaments are able to make effective use of their new powers through relations to other national parliaments, the European Parliament and the Commission. The article presents the findings of quantitative and qualitative research into the co-operation and co-ordination activities of national parliaments in different policy areas and detects four role types of national parliaments’ influence: policy-shapers, veto-players, spectators, and outsiders. The latter two roles are associated with a lack of interest in becoming involved. The extent to which they act as the former, veto-players or policy-shapers, depends on other factors: first, the degree of co-ordination at a transnational level is decisive; second, the EP’s incentives to co-operate are driven by its own, at times competing, interests. Finally, the chances of effective influence increase with the Commission’s willingness to co-ordinate in a timely fashion. In the conclusion the article explores the implications of the variation in national parliaments´ roles in EU policy-making for multilevel parliamentary democracy in the EU.
