The focal point of this paper is to research under which conditions can the currency clause, which is explicitly permitted by Croatian law, be null and in which way does its' nullity affect the performance of the contract and its' capacity to remain in full force and effect. The analysis shall be performed by researching the issue of unfairness of the currency clause indexed to the Swiss franc in consumer credit agreements concluded in the approximated period from 2004 to 2008. Specifically on that practical issue it is possible to analyse all the criteria which need to be met in order for the currency clause to be void. The criteria for nullity of contractual clauses in consumer contracts, which includes the currency clause, are set by the Council Directive 93/13/EEC on unfair terms in consumer contracts, as well as in the Consumer Protection Act from 2003 by which it was implemented. Due to the circumstance that the criteria are broadly determined, the research turns towards European Court case-law for clarification and specification of the criteria, so that they could be properly applied on the researched case. In addition, a review will be made of the existing Croatian judgments during the course of court proceedings in the „Franak case“ for analysis if those judgments, and if so in which measure, deviate from the European Court case-law in its' interpretation of the criteria for determining nullity of contractual clauses. In conclusion, it will be specified in which way could the High Commercial Court of the Republic of Croatia decide in the repeated proceedings in a way that correctly interprets the criteria for unfairness of contractual clauses in accordance with the existing European Court case-law.