"Curriculum for the subject Croatian language for primary schools and gymnasiums in the Republic of Croatia" passed in 2019, so the Ministry of Science and Education has issued a public call for applications for approval of the use of textbooks in schools and inclusion of textbooks in the "Catalog of Approved Textbooks" for school years 2019/2020, 2020/2021 and 2021/2022, including new Croatian language textbooks. The topic of this thesis is high school textbooks of the Croatian language before and after the reform, more precisely the old textbooks "Fon-Fon" (editions from 2015 to 2017) and new textbooks "Fon-Fon" (editions from 2019 to 2021). The publisher is Profil Klett. The first, theoretical part of the thesis consists of two main chapters. The first chapter is dedicated to the textbook as an educational tool (definition of the term, didactic-methodical design, types of textbooks, the legal documents). The second part deals with the relationship between the former curriculum (Croatian: "nastavni plan i program") with the new curriculum, gives a brief overview of curricular reform in the Republic of Croatia, and compares the old "Croatian Language Curriculum for Gymnasiums" (1994) and the new "Curriculum" (2019) from different aspects. The empirical part brings the course and results of the research, analyzing the conceptual features of the textbook, the representation of the texts of the different functional styles and types of tasks for repetition and exercise concerning their focus on students and stimulated language activities.