The aim of this thesis is to examine the issues of one of the institutes of a real intensification of obligatory relationship i.e. liability for material defect in items. In accordance with the specified, at the very beginning the most important concepts and terms relevant for this paperand changes caused by passing of the new Law on Obligations have been explained. Furthermore, general assumptions of liability have been analyzed; a difference between visible and hidden defects has been explained, as well as cases of existence and a lack of liability of the seller. In the thesis duties and obligations of buyers have been described minutely, while in the chapter under the title Substance of responsibility the rights of the buyer have been systematized and listed. Likewise, all deadlines relevant to realisation of these rights, as well as the very institute of guarantee have been analyzed. The last topic of this work covers Protection of consumers according to the Directive of the European Union and our Consumer Protection Law.