The aim of this thesis is to define the lexical units that are most vulnerable to the interference caused by lexical nonequivalence between Czech and Spanish vocabulary. The thesis is divided into the theoretical and the practical part. In the theoretical part the author introduces the issue of lexical nonequivalence in general and on the basis of the studied literature creates a linguodidactic classification of lexical nonequivalence. Specific cases of lexical nonequivalence are identified and explained in the practical part of the thesis based on an analysis of Spanish vocabulary of the textbooks Aventura 1,2, Nuevo Ven 1 and Nuevo Ven 2 (the first 8 lessons), which corresponds to the second stage of basic education, ie up to level B1. The interference caused by lexical nonequivalence is identified on the basis of the author´s own experience in teaching Spanish, therefore, both spoken and written expression of students are submitted to analysis.