This study is a linguistic investigation of four preschool-aged Italian children with SLI (4:5–5:9), using more than one linguistic modality, with the aim of analyzing their performance with relative clauses (subject and object relatives). Linguistic abilities in comprehension and production do not overlap in children with SLI and in typical developing children, revealing characteristics related to distinctions between the modalities as well as certain properties of language impairment. While comprehension by children with SLI is comparable to age-matched peers, their production shows a wider range of variation, providing a useful source with which to evaluate syntactic competence. Typically developing children adopt many different strategies to avoid the more complex, object relative clauses. Children with SLI, however, do not and are unable to construct any kind of relative clause.