The dissertation examines the legal regulation in the field of consumer protection against unfair commercial practices. The dissertation discusses the reasons which determined the need to adopt legal instrument, establishing consumer protection against unfair commercial practices, the development of the fair trading principle, its features formulated in the jurisprudence of the Court of Justice of the European Union, instruments which on the European Union law level in a fragmentary way harmonised particular aspects concerning fair trading. The research focuses on the analysis of the Directive 2005/29/EC of the European Parliament and of the Council of 11 May 2005 concerning unfair business-to-consumer commercial practices in the internal market (Unfair Commercial Practices Directive), emphasizing its specificity in comparison with other consumer protection instruments adopted in consumer protection field. It comprehensively examines the provisions of the Directive, reveals the structure of the prohibition of unfair commercial practices, control mechanism and its scope of application. The object of the research also includes the analysis of Lithuania’s as a European Union Member State’s ability to transpose the provisions of the Unfair Commercial Practices Directive into the national law. Having in mind that Lithuania has not avoided implementation errors, the author provides detailed recommendations for the national legislator suggesting the potential solutions for improving the transposition of the provisions of the Unfair Commercial Practices Directive into the national law and in such way creating conditions for the proper interpretation and application of law and ensuring proper consumer protection in this field. The analysed subject is relevant and in a wider – European Union consumer law context. Author pays considerable attention to the examination of the possible impact of the Unfair Commercial Practices Directive on the application and interpretation of the provisions of certain legal acts, establishing the contractual rights of the consumers, as well as the correlation between Directive and contractual consumer protection instruments.