When two or more people witness an event together, the event report from one person can influence others' reports. In the current study we examined the role of age and motivational factors on peer influence regarding event reports in adolescents and young adults. Participants (N=249) watched a short video of a robbery then answered questions with no co-witness information or with information believed to be from a co-witness. Public and private response conditions were included to explore motivations for peer influence. Co-witness information influenced participants' responses, although the effect was equally strong in the private and the public co-witness conditions. Peer influence on event reports was steady across a large age range (11- to 25-year-olds).