New research at the University of Tasmania suggests it may be that too many children are being diagnosed with Attention Deficit Hyperactivity Disorder (ADHD) and being prescribed Ritalin.

The research also shows the usage of Ritalin in Tasmania is among the highest in the nation per capita.

It also suggest a link between ADHD and another motor coordination condition, Developmental Coordination Disorder (DCD).

Bruno Cayoun, of the university's School of Psychology, says movement problems found in some children with ADHD are related to attention span, while in other children they are related to DCD.

He says 29 per cent of children diagnosed with ADHD also fit the criteria for DCD.

Mr Cayoun says the finding is important, as the treatment for both is different - medication is prescribed for ADHD and physical exercise for DCD.

Mr Cayoun says it is possible too many children are taking Ritalin, and while Perth has the highest usage in Australia, Tasmania is not far off.

Mr Cayoun believes there is an overlap in the diagnostic criteria for both conditions, and a review of the clinicians' diagnostic manual is needed.

"This is not an issue for the clinician to review their work, it's really an issue for those who produce the manual to review what the criteria are," he said.

"We have excellent clinicians here, but we all rely on this criteria for diagnosis."