Background: The lexical quality hypothesis proposes that successful reading comprehension requires high quality lexical representations, which allow for efficient retrieval. These retrieval operations have however not been specified. Methods: We investigated the contribution of semantic retrieval to reading comprehension in 119 Dutch children in the upper grades of primary school, while taking decoding skills and vocabulary size into account in a longitudinal design. By using verbal fluency tasks, we measured retrieval in line with the structural organisation of the mental lexicon and additionally, a more controlled search through the mental lexicon. Results: Semantic retrieval assessed in grade 5 accounted for variance in reading comprehension in grade 6, in addition to variance accounted for by vocabulary size and reading comprehension in grade 5. Conclusions: The ability to search through the mental lexicon, along the lines of its hierarchical structure, is important for children's reading comprehension development in the upper primary grades.