Verb inflectional morphology and prepositions are loci of difficulty for bilingual children with typical language development (TLD) as well as children with Specific Language Impairment (SLI). This paper examines errors in these linguistic domains in these two populations. Bilingual English-Hebrew and Russian-Hebrew preschool children, aged five to seven, with TLD, and age-matched monolingual Hebrew-speaking children with SLI, were tested using sentence completion and sentence imitation tasks in their L2 Hebrew. Our findings show that, despite the similarity in the locus of errors, the two populations can be distinguished by both the quantity and the quality of errors. While bilingual children with TLD had substitution errors often motivated by the first language, most of the errors of monolingual children with SLI involved omission of the whole morpheme or feature reduction. This difference in the nature of the errors is discussed in terms of bilingual processing vs. impaired representation.