The objective of this article is to explain the differing levels of support achieved by Eurosceptic parties in European Parliament elections in Poland for the years 2004, 2009, and 2014. Taking into account the specificity of EP elections, which in theory assign greater importance to European issues, the analysis is conducted using the “Eurosceptic opportunity structure”, which is composed of: political space, social attitudes towards integration, and the external factor (the dynamics of the European integration process). Additionally, there is analysis of the attitudes of Eurosceptic parties standing for election. The analysis demonstrates that the supply and demand sides created a similar opportunity structure for Eurosceptic parties in all three elections, while the external factor provided those parties with greater possibilities in 2004 and 2014. Analysis of the attitudes of Eurosceptic parties, however, indicated that they had greater chances to attract voters by invoking the European question in 2004 and 2014. The combination of these conclusions along with the support received by Eurosceptics in particular elections confirms the validity and the explanatory function of the adopted assumptions, while emphasizing the fundamental role played by the parties themselves in the examined aspect. Nonetheless, to confirm the primary assumption and state with more certainty the impact of the European issue on electoral behaviours, more in-depth analysis is necessary.