Background: English-speaking children with specific language impairment (SLI) perform more poorly than their typically developing peers in verbal working memory tasks where processing and storage are simultaneously required. Hungarian is a language with a relatively free word order and a rich agglutinative morphology. Aims: To examine the effect of linguistic structure on working memory performance. It was examined whether syntactic complexity has a larger impact on working memory performance than sentence length in Hungarian-speaking children, similar to the findings in English speaking children. Methods & Procedures: In Experiment 1, performance accuracy was measured with two linguistic span tasks that included stimuli with varying sentence length and syntactic complexity. Experiment 2 examined the impact of sentence length and morphological complexity on working memory performance. Outcomes & Results: Children with SLI performed more poorly than their age-matched peers in all working memory tasks. Their error patterns differed from those of children with typical language development. Children with SLI produced a high number of interference errors that indicate poor executive functions. The findings were compared with previous results of English-speaking children. Complexity affected working memory performance accuracy differently across languages. In English, it was the increase of syntactic complexity that resulted in a decrease in performance accuracy, whereas in Hungarian, it was the morphological complexity that had a large impact on working memory performance. Conclusions: Working memory performance depends on the linguistic characteristics of the language tested. In both English- and Hungarian-speaking children, complexity has a larger effect on verbal working memory performance than the length of the stimuli. However, complexity affects working memory performance accuracy differently across languages. (Contains 2 figures and 6 tables.)