The FIDIC Books made by the International Federation of Consulting Engineers provides different contract samples for construction projects, depending on the type of the project, with the primary aim of summarising best practice and proportionate risk-sharing. FIDIC Books are considered to be the most popular contractual conditions worldwide in connection with construction projects. The Yellow Book is the second most commonly used contract sample, the essence of which is that the contractor’s obligation covers both planning and building. In case of construction contracts lack of conformity is one of the most common breach of contract, so it is of particular importance for the parties to know what warranty rights the customer can exercise and under what conditions. Warranty rights are also provided for in the Yellow Book, which is why in certain cases there is competition between the Hungarian Civil Code and the Yellow Book, which makes it difficult to draw up a contract, bearing in mind that the rules of the Yellow Book are often difficult to interpret because of their Anglo-Saxon origin. After outlining the views on the interpretation of the Yellow Book, the study will examine the relevant rules of the Hungarian Civil Code and the Yellow Book from a comparative legal point of view, with a view to identifying the cases of lack of conformity under the Yellow Book, the available warranty rights and the procedures for their exercise by the customer. At the end of each chapter, the author presents the rules of the Hungarian Civil Code and the Yellow Book in comparative tables, and concludes the study by outlining the advantages and disadvantages for both the customer and the contractor.