The present study investigated the effect of self-reported vividness of visual imagery on the ability to discriminate between memories derived from two external sources of information. Subjects were shown a film of a crime and were then given a written description of the event which included information not seen in the film. In a source monitoring task, high and low imagers were found to be equally proficient in recognizing items as previously presented, but high imagers were poorer at discriminating the source of items based on the written description. This finding is considered in terms of possible encoding and retrieval differences resulting from imagery vividness. The role of vivid visual imagery as a variable underpinning confusions in eyewitness testimony is discussed.