The advantage in person memory of impression formation over memory task instructions is shown to extend to the eyewitness identification paradigm. Instructions to form an impression of target persons led to more accurate identifications in subsequent photo line-ups than explicit instructions to memorize the targets (Experiment 1). Prior knowledge that a crime was going on did not affect performance. Two confounded components of the successful instruction condition were decomposed in Experiment 2, showing that the enhanced performance is due to the impression task proper, rather than the absence of explicit memory instructions. Analyses of hits and false alarms revealed that the positive influence of impression formation on discrimination performance was due to a genuine enhancement in discrimination ability rather than merely a shift toward a stricter response criterion. Experiment 3 provided some evidence to suggest that eyewitness performance can even be influenced by recontextualization efforts and impression judgments at the time of retrieval. Copyright © 2008 John Wiley & Sons, Ltd.