One in 20 schoolchildren is said to suffer from a form of ADHD
Allowing children with attention-deficit disorders to "queue jump" at theme parks could be doing them more harm than good, one expert suggests.
Children with attention deficit hyperactivity disorder (ADHD) are given passes in most theme parks if they can prove they have the condition.
This may reduce the stress of waiting, which they find very difficult.
But Professor Katya Rubia, of London's Institute of Psychiatry, said it was important they learned to do so.
The Disability Discrimination Act puts a duty on attractions such as leisure parks to accommodate the needs of all visitors: this can include those with ADHD if they provide the necessary documentation.
ADHD is now the most common childhood-onset behavioural disorder.
Those affected have a greatly reduced ability to maintain attention without being distracted and find it difficult to control what they are doing or saying.
At least one in 20 schoolchildren - 360,000 in total - is thought to have some degree of attention deficit hyperactivity disorder (ADHD), but some critics argue unruly behaviour is being overly medicalised.
Professor Rubia who has researched ADHD said her work showed such children did have serious problems with understanding time and an inability to delay a reward.
"This is clearly a medical condition, but it isn't right to bring them up in a system where they never have to wait. You're not making it any better for them - this is something they can be helped to learn.
"I can see why parents might like it, but in the long term you are not doing the child any favours. This is a condition which we can improve, and learning to wait should be part of that process."
The fact that ADHD children and carers can avail themselves of this scheme has sparked some controversy since appearing in the Times Educational Supplement.
But the chief executive of The National Attention Deficit Disorder Information and Support Service said there was nothing controversial about it.
"These are children with a disability who cannot wait. You cannot teach someone who is crippled to walk, someone who is deaf to hear," says Andrea Bilbow. "They have a 30% maturity lag, and are emotionally younger than their peers.
"This is no different to these children being allowed to go ahead in the dinner queue at school.
"What people need to remember is that it doesn't just make it easier for the child and their carers, it's better for everyone in that queue too."