Previous reviews and meta-analyses that addressed abnormal Stroop interference in attention-deficit/hyperactivity disorder (ADHD) yielded mixed results. The authors of the present study argue that the inconsistencies may reflect the problematic nature of 2 frequently used methods to quantify Stroop interference-the difference score and Golden's method (C. J. Golden, 1978). Golden's method correction for base-word reading is inadequate, and the difference score is sensitive to the nature of the outcome variable. The latter can be remedied with a ratio score. Contrasting previous meta-analyses, this meta-analysis covers all age groups and all Stroop test variants, and it excludes studies using the Golden quantification method. Mean effect sizes for interference in ADHD as quantified by difference scores relative to control scores were 0.24 across all studies but 1.11 for time-per-item studies; outcome variable was a significant moderator variable, reflecting the sensitivity of the difference score to this variable. Consistency analysis of ratio scores across 19 studies reveals more interference for the ADHD groups relative to the control groups. It is concluded that interference control is consistently compromised in individuals with ADHD.