Research background: The Post-Lisbon EU aims at smart, sustainable, and inclusive growth on the single internal market, as indicated by the Europe 2020. The interplay of the competition and consumer protection on such a market is subject to harmonization. The Unfair Commercial Practices Directive has been made in order to achieve a full harmonization in this respect in 2007. However, EU member states share different social, political, legal and economic traditions and their approaches to unfair competition, in particular if committed via parasitic commercial practices, are dramatically diverse. In such a context, is it feasible, effective and efficient to install a full harmonization? Purpose of the article: The primary purpose of this article is to describe and assess approaches to unfair competition, in particular if committed via parasitic commercial practices, by the EU law and EU member states law. The secondary purpose is to study and evaluate possibilities for the feasible, effective and efficient harmonization, or their lack. Methods: The cross-disciplinary and multi-jurisdictional nature of this article, and its dual purposes, implies the use of Meta-Analysis, of the critical comparison of laws and the impact of their application, to the holistic perception of historical and national contexts, and to case studies. The primary and secondary sources are explored and the yield knowledge and data are confronted with the status quo. The dominating qualitative research and data are complemented by the quantitative research and data. Findings & Value added: The EU opted for an ambitious challenge to install via the Unfair Commercial Practices Directive a full harmonization of the regime against unfair commercial practices, including parasitic ones. The exploration pursuant to the duo of purposes suggests that the challenge is perhaps too ambitious and that the EU underestimated the dramatic diversity of approaches to unfair commercial practices, especially parasitic ones.