To date, research investigating the similarity among lineup members has focused on adult eyewitnesses. In the present research, children made identifications from lineups containing members of lower or higher similarity to a target person. In Experiment 1, following a live interaction, children's (6–14 years) correct identification rate was reduced in higher‐similarity relative to lower‐similarity lineups. In Experiment 2, children (6–12 years) and adults watched a video containing a target person. Again, higher‐similarity lineup members reduced children's correct identifications; however, similarity had no effect on adults' correct identification rate. Although children benefited from lower‐similarity lineups when the target was present, lower‐similarity lineups generally increased misidentifications of an innocent suspect when the target was absent. Thus, increasing similarity in lineups for children had a cost on target‐present lineups and a benefit on target‐absent lineups. Copyright © 2014 John Wiley & Sons, Ltd.