The electoral behaviour of Portuguese citizens is marked by a major difference, concerning the turnout rates, between elections for the various national political bodies and elections for the European Parliament. Portugal has one of the lowest voting turnout in Parliament elections for the European Union. Paradoxically, opinion surveys indicate that the Portuguese are among the peoples who most support the European construction process. This text seeks understand the reasons for the behaviour of Portuguese voters. Motives approached include citizens' degree of identification with the EU political system, public perception of how the system works and dominant trends in the reform of ways to represent States and citizens in European Union institutions