Hungarian is a language with morphological case marking and relatively free word order. These typological characteristics make it a good ground for testing the crosslinguistic validity of theories on processing sentences with relative clauses. Our study focused on effects of structural factors and processing capacity. We tested 43 typically developing children in two age groups (ages of 4.11-7.2 and 8.2-11.4 years) in an act-out task. Differences in comprehension difficulty between different word order patterns and different head function relations were observed independently of each other. The structural properties causing difficulties in comprehension were interruption of main clauses, greater distance between the verb and its arguments, accusative case of relative pronouns, and SO head-function relations. Importantly, analyses of associations between working memory and sentence comprehension revealed that structural factors made processing difficult by burdening components of working memory. These results support the processing accounts of sentence comprehension in a language typologically different from English. (Contains 5 tables and 6 figures.)