Subject and object relative clauses have been studied from the point of view of language acquisition and adult sentence processing. In the adult sentence processing literature, subject relative clauses (RCs) are read faster than object RCs (e.g., Frauenfelder et al. 1980 for French; King and Kutas 1995 for English; Schriefers et al. 1995 for Dutch). Similarly, children understand and produce subject RCs earlier and with greater accuracy than object RCs in a variety of languages with head-initial relative clauses, as English, Hebrew and Italian. These findings cannot be a coincidence but reflect the fact that what children acquire first is also easier to process by adults. In this article, we support this observation by investigating subject and object RCs in children and adults speaking French and Italian. These languages display subject and object relatives as in (1), but they also have a type of object relative in which the subject is postverbal. We replicate the observation that subject relatives are easier than object and show that object relatives as in (1b), with the embedded subject in preverbal position are easier than those with the embedded subject in postverbal position, both for children and adults. We offer an account of these findings in terms of Fodor and Inoue's (2000) diagnosis model in light of the fact that acquisition involves processing.