Objective We aimed to investigate the long-term effects of atomoxetine on growth in Korean children and adolescents with attentiondeficit/hyperactivity disorder (ADHD). Methods The medical records of 82 subjects (mean age, 9.0±2.0 years; 64 boys) with ADHD treated with atomoxetine for at least 1 year at the Department of Psychiatry at Asan Medical Center were retrospectively reviewed. Height and weight data were prospectively obtained and retrospectively gathered and converted to age- and gender-corrected z scores using norms from Korean youths. Growth changes were analyzed using random coefficients models with changes in height or weight z scores as the dependent variables. Results Height z scores significantly decreased during the treatment period (β=-0.054, p=0.024). Height z scores decreased during the 1st year of treatment (β=-0.086, p=0.003), but did not change after the 1st year. Weight z scores did not change significantly during treatment(β=0.004, p=0.925). Conclusion Our results suggest that long-term atomoxetine treatment may be associated with deficits in height growth in Korean youths, although this effect was minor and tended to be attenuated over the first year. Because of the limitations of this study such as retrospective design and selection bias, further prospective studies are needed.