In this study, we investigate children's and adults' relative clause attachment preferences in sentences such as "The student photographed the fan of the actress who was looking happy." Twenty-nine 6- to 7-year-old monolingual English children and 37 adult native speakers of English participated both in an auditory questionnaire study and in an online, self-paced listening experiment. Whereas the adult group's attachment preferences were influenced by the type of preposition joining the 2 potential antecedent noun phrases (NPs) (of vs. with), children's online attachment preferences varied depending on their listening span: Children with a relatively high listening span showed a preference for NP1 attachment irrespective of the type of preposition involved, whereas the children with a low span showed a general tendency toward NP2 disambiguation. We argue that (i) when resolving modifier attachment ambiguities during online processing, children primarily rely on structural information and (ii) the observed differences between children and adults, as well as those found between the two span groups, reflect working memory differences rather than differences in the parser.