Background: This study investigated the relationship between phonological and syntactic disorders of French-speaking children with specific language impairment in production. Aims: To compare three theories (pure phonological theory, surface theory, and mapping theory) of language developmental disorders, all of which view phonological difficulties as the main reason for the children's problems. Methods & Procedures: The linguistic parameters (salience, phonological complexity, syntactic complexity, lexical/functional word, semantic/syntactic weight) that are fundamental to these theories were identified. The validity of these parameters was then tested against the phonological and syntactic results obtained by children with specific language impairment and control children. Nine syntactic categories were tested. Outcomes & Results: Phonological complexity was the only parameter whose importance was confirmed, and this was only for phonological performance. Syntactic complexity did not correlate significantly with children's difficulties. Phonological salience did not correlate with phonological performance but was related to syntactic performance for French-speaking children. Mixed results were obtained for the other parameters, including negative correlations, which may call for different explanations. Conclusions: No theory fully explained the observed outcomes. Pure phonological theory was the most parsimonious, but could not explain all the results, in particular not the results with respect to grammar. (Contains 7 tables.)