Written communication of children with dyslexia can be observed through the analysis of discourse production at the microstructural level. Discourse is defined as language that extends beyond individual sentences (Ulatowska et al., 1983) and is shaped by the communicative goal, leading to the distinction of various discourse genres. Mastery of narrative and expository genres is crucial in education, as it plays a significant role in an individual's academic success (Hall-Mills, 2010). The aim of this paper was to compare the quality of written language samples at the microstructural level in children with dyslexia in two discourse genres, narrative and expository. The written texts of children with dyslexia under the age of 15 (N = 89) were taken from the Croatian Corpus of Non-Professional Written Language (HKNPJ; Kuvač Kraljević et al., 2021), coded according to the rules of the Codes for the Human Analyzes of Transcripts (CHAT) and then processed in the computer program Computerized Language Analysis (CLAN). Linguistic measures of productivity, syntactic complexity and vocabulary diversity were calculated for each written sample. The obtained results indicated greater productivity in narrative texts, but greater lexical diversity in expository texts. On two linguistic measures of syntactic complexity (mean length of clause and clause density), significant differences between genres were observed, however, the direction of the differences was opposite. In both discourse genres, children with dyslexia made mistakes to the same extent and in the same way. Errors were observed on the phonological, morphosyntactic and semantic level, as well as errors caused by not respecting the orthography of the language. This paper provides a contribution to foreign and Croatian research of the written expression in students with dyslexia. It also highlights the need for further research to gain a deeper understanding of the writing characteristics of this population. The knowledge obtained through this research provides guidelines for working with children with dyslexia, emphasizing the importance of producing written discourses of various functions that would provide a more detailed insight into the child's language abilities. These guidelines are useful in both speech therapy and educational settings.