Poland's lurch to the nationalist right in the first election to be influenced by Europe's refugee crisis is sending shudders of anxiety through the EU leadership in Brussels, where officials expect a prickly relationship.
EU officials have not forgotten the first time Jaroslaw Kaczynski's conservative Law and Justice (PiS) party ran the biggest member state in Central Europe in 2005-07.
Warsaw held up ratification of the EU's Lisbon Treaty, fought for more voting power in the bloc, and obstructed the launch of partnership talks with Russia.