Objective: The main aim of the present study is to investigate the short-term cognitive effects of computer games in children with different psychiatric disorders and normal controls. Method: One hundred one children are recruited for the study (aged between 9 and 12 years). All participants played a motor-racing game on the computer for 1 hour. The TBAG form of the Stroop task was administered to all participants twice, before playing and immediately after playing the game. Results: Participants with improved posttest scores, compared to their pretest scores, used the computer on average 0.67 plus or minus 1.1 hr/day, while the average administered was measured at 1.6 plus or minus 1.4 hr/day and 1.3 plus or minus 0.9 hr/day computer use for participants with worse or unaltered scores, respectively. According to the regression model, male gender, younger ages, duration of daily computer use, and ADHD inattention type were found to be independent risk factors for worsened posttest scores. Conclusion: Time spent playing computer games can exert a short-term effect on attention as measured by the Stroop test. (Contains 4 tables.)