Twenty 5 to 15-year-old children with Autism Spectrum Disorders (ASD) were assessed on their ability to understand complex syntactic structures and to attribute a false belief to a protagonist. Syntax tasks included relative clause and wh-question comprehension, as measured by participants' correct designation of one of three characters. Complement clauses were measured with a truth-value judgment task requiring participants to assess the truth of a puppet's utterance. These syntactic structures are situated in the highest layer of the syntactic tree (CP), and as such we expected ASD children to show difficulty in understanding them, because of a purported syntactic deficit stemming from prolonged truncation (Durrleman & Zufferey, 2009). Furthermore, we tested the hypothesis that ASD children's syntax would follow the pattern predicted by a measure of syntactic complexity based on Relativized Minimality...