This study examines prosodic disambiguation in child-directed (CD) speech. Twenty-four mothers addressed syntactically ambiguous sentences to their 2;0 to 3;8 year old child and to an adult confederate. Twenty-four non-mothers addressed an imaginary toddler and an imaginary adult. We found that only mothers increased pitch and produced the CD-typical pitch excursions when addressing their children. In contrast, non-mothers, but not mothers, used prosodic disambiguation in CD speech, which was corroborated by a forced choice test in which 48 listeners judged the intended meaning of each sentence. The results suggest that if speakers express genuine positive affect, they tend to emphasise affective prosody at the expense of linguistic prosody. In the case of CD speech, this communication strategy may be more effective as it serves to elicit the childs attention.