This study addresses the question of the separate contribution of tonal and duration cues in prosodic boundary marking and their effect in syntactic parsing in French. We used pairs of Noun Phrases whose segmental structure was identical but differing in the potential placement of an Accentual Phrase (AP) or Intermediate Phrase (ip) boundary at their right edge. We artificially manipulated the acoustic cues at AP/ip boundaries to obtain a set of stimuli marked either by one type of cue (either tonal or duration cues) or by both indices. In a two forced-choice completion task (PP-choice or VP-choice), participants gave more PP responses when an AP boundary was marked, either by both cues or only by duration indices, relative to when an ip boundary was present. Specifically, for the ip-boundary level to be identified, participants needed the presence of both types of cues to correctly complete the sentence. These results offer a new understanding of the separate role of acoustic cues in prosodic boundary marking.