Our goal is to investigate the semantics of French parenthetical clauses and determine the type of content they express: is it an assertion, a presupposition or an implicature ? A distinction between two subtypes of parenthetical clauses is introduced: on the one hand, parentheticals which convey Speaker’s comment and thus are analyzed as conventional implicatures; on the other hand, parentheticals that are used to report a speech or a thought, and which convey both an at-issue content and a presupposition. The analysis of the two subtypes of parentheticals is based on the idea that there are two distinct reference processes: description and imitation. Quotation is assumed to be a special case of imitation, and imitation in itself is analyzed as triggering a presupposition: it presupposes that what is imitated exists.