Background: Imitation, a key vehicle for both cognitive and social development, is often regarded as more difficult for children with autism spectrum disorders (ASD) than for children with Down syndrome (DS) or typically developing (TD) children. The current study investigates similarities and differences in observed elicited, spontaneous and deferred imitation using both actions with objects and gestures as imitation tasks in these groups. Methods: Imitation among 19 children with autism was compared with 20 children with DS and 23 TD children matched for mental and language age. Results: Elicited imitation resulted in significantly lower scores for the ASD group compared with the other two groups, an effect mainly carried by a low level of gesture imitation among ASD children. We observed no differences among the groups for spontaneous imitation. However, children with ASD or DS displayed less deferred imitation than the TD group. Proneness to imitate also differed among groups: only 10 (53%) of the children with autism responded in the elicited imitation condition compared with all children with DS and almost all TD children (87%). Conclusions: These findings add to our understanding of the kind of imitation difficulties children with ASD might have. They also point to the necessity of not equating various imitation measures because these may capture different processes and be differently motivating for children with autism.