Individuals with Autism Spectrum Disorders (ASD) have difficulties with imitation, though the nature of these remains unclear. In this study, involving 28 preschoolers with ASD (M age?=?48 months; 90 % male), 17 matched children with Global Developmental Delay (GDD group; M age?=?44 months; 53 % male) and 17 typically developing children (TD group, M age?=?52 months; 65 % male), we found that preschoolers with ASD 1) imitate less frequently than both typically developing children and children with GDD; 2) when they do imitate, their imitation is less accurate than that of TD children but similar to that of children with GDD; 3) unlike participants in both comparison groups, preschoolers with ASD use emulation more often than imitation when copying others' actions; 4) they spend less time looking at the model's face and more time looking at her actions; and 5) attentional, social and executive factors underlie different aspects of imitation difficulties in this population. Implications for developmental models of autism are discussed.