This dissertation investigates the comprehension of subject and object relative clauses and wh-questions in French and Romanian monolingual typically-developing children, as a means to identify the types of information (i.e. morphosyntactic, semantic) that lead children to successfully interpret complex linguistic structures. It brings evidence in favour of the idea that children's selective difficulties with object dependencies stem from intervention effects amenable to effects of syntactic locality determined by the principle of Relativized Minimality (Friedmann et al., 2009; Rizzi, 1990, 2004, 2013; Starke, 2001). Moreover, the findings illustrate that, under specific conditions, intervention effects can be modulated or by-passed by (i) morphosyntactic features such as number, case, animacy; (ii) language-specific properties (like the presence of a post-verbal subject in Romanian); (iii) the degree of specificity of the moved object (whether the object has a more or less specific reference).