Background: Atomoxetine is a central norepinephrine reuptake inhibitor used to treat attention deficit/hyperactivity disorder. The effects of atomoxetine on cardiovascular functions and QT dispersion in children with attention deficit/hyperactivity disorder have not been previously reported. The aim of this study was to analyse cardiovascular functions and QT dispersion on the surface electrocardiogram of children with attention deficit/hyperactivity disorder during atomoxetine therapy. Methods: A total of 40 children - with a mean age of 8.6 plus or minus 2.3 years and a median age of 11 years; ranged from 8 to 14 years - with attention deficit/hyperactivity disorder - with six girls and 34 boys - were included in the study. We recorded the mean systolic and diastolic blood pressure, heart rate, corrected QT interval, QT dispersion, and left ventricular systolic functions at baseline and 5 weeks after atomoxetine therapy. Results: Atomoxetine decreased baseline mean systolic and diastolic blood pressure; baseline mean heart rate decreased; and baseline mean corrected QT interval and QT dispersion mildly increased. Atomoxetine decreased baseline mean ejection fraction and baseline mean shortening fraction. Conclusion: The results of our study suggest that atomoxetine does not cause clinically significant alterations in QT dispersion, systolic and diastolic blood pressure, heart rate, corrected QT interval, and left ventricular systolic functions during short-term treatment in children with attention deficit/hyperactivity disorder. © 2011 Cambridge University Press.