Background:It is difficult to determine the usefulness of distraction to decrease children's distress behavior and pain during medical procedures because many studies use very small samples and report inconsistent findings.Objectives:To investigate the mean effect sizes across studies for the effects of distraction on young children's distress behavior and self-reported pain during medical procedures.Method:Hunter and Schmidt's (1990)procedures were used to analyze 16 studies (totaln= 491) on children's distress behavior and 10 studies (totaln= 535) on children's pain.Results:For distress behavior, the mean effect size was 0.33 (±0.17), with 74% of the variance accounted for by sampling and measurement error. For pain, the mean effect size was 0.62 (±0.42) with 35% of the variance accounted for. Analysis of studies on pain that limited the sample to children 7 years of age or younger (totaln= 286) increased the amount of explained variance to 60%.Conclusions:Distraction had a positive effect on children's distress behavior across the populations represented in this study. The effect of distraction on children's self-reported pain is influenced by moderator variables. Controlling for age and type of painful procedure significantly increased the amount of explained variance, but there are other unidentified moderators at work.