The paper examines the theory of horizontal effect of fundamental rights and freedoms, known also as Drittwirkung. It introduces relevant doctrines in Germany and Poland in order to then focus on the EU theory shaped in the case law of the European Court of Justice, most notably in the landmark Viking Line judgment. Highly formalized German approach is confronted with more flexible attitudes developed by the ECJ and in Poland. The paper demonstrates the exceptionality of horizontal effect and its links with the principle of effectiveness which lies at the core of the modern systems of human rights protection. It also argues that the distinction between direct and indirect effect can be blurred, may depend on the available causes of action and consequently should not be overrated.