The condition is linked with inattention, hyperactivity and strong impulses and is thought to affect one in 20 under-18s.
According to the scans, suspected ADHD sufferers have an overall smaller brain size, which also goes for five specific regions of the brain, including the amygdala - responsible for regulating emotions.
"This study represents an important contribution to the field by providing robust evidence to support the notion of ADHD as a brain disorder with substantial effects on the volumes of subcortical nuclei", they wrote.
New study suggests that children with attention-deficit hyperactivity disorder (ADHD) have different brain structure from those people without ADHD.
Hoogman points to other conditions where brain size differences are commonplace, such as major depressive disorder (MDD). ADHD is more than "just a hard child", something you hear all too often about children with ADHD'.
"We hope that this will help reduce stigma that ADHD is "just a label" for hard children or caused by poor parenting", said the study's leader author, Martine Hoogman of Radboud University Medical Center in the Netherlands, in a statement reported by AFP.
"These differences are very small - in the range of a few percent - so the unprecedented size of our study was crucial to help identify these", she said.
The study examined 1,713 people with ADHD and 1,529 people without, ranging in age from 4 to 63 years old. "Future meta-analyses and mega-analyses will need to investigate medication effects as well as the developmental course of volumetric differences in this disorder".
The affected regions include the amygdala, which is involved in the regulation of emotion.
This is not the first time that brain volumes have been linked to ADHD but previous studies had small sample sizes that rendered results inconclusive.
By being able to point to measurable differences in the brains of those with ADHD, the ENGIMA scientists hope their study will also help the general public better understand the disorder. The researchers therefore assume that a delay in the development of the brain is a characteristic of ADHD.
Dr. Jonathan Posner, associate professor of psychiatry at Columbia University in NY, was not involved in the study. The difference between the brains of those who have ADHD and those of the ones who don't is small.