This graduate thesis deals with the use of adjectives in written compositions of elementary school pupils. The main aim was to investigate how often students use the adjectives in written compositions on a particular topic and want to determine whether the use of adjectives differs with motivation. As far as theories are concerned, the introductory part describes the subject of Croatian language, as the most prominent element of elementary education. Furthermore, the paper describes linguistic expression and linguistic activity as well as language development itself. More specifically, adjectives are described as type of words, grammatical categories of adjectives, and the role of adjectives such as attributive and predicate. At the very end, there is the developmental course of mastering adjectives. This graduate thesis consists of the research detailed in Chapter 8. The research was conducted on a sample of 89 third and fourth grade students of the elementary school of Antun Branko Šimić. The students were supposed to write a composition on a particular topic, and the themes written in the composition were My Friend in the Third, and My Classroom in the Fourth Class. In one third and one fourth grade, experimental motivation was carried out, and in the other four classes control motivation. The topics of the written compositions were My Friend in the Third, and My Classroom in the Fourth Class. The research showed that usage of adjectives can, be influenced by motivation, as it can be seen from the results of third graders. Furthermore, comparison between third and fourth graders revealed that age of pupils plays significant role in number of adjectives used.