A child is being disruptive in the classroom - not paying attention, talking and annoying those around him. Does he have Attention-deficit hyperactivity disorder? Or is he simply badly-behaved?
It is a question many parents may have asked themselves about their child or about someone else's.
But experts say if parents think their child may have ADHD, they are probably right.
Bad behaviour is intermittent and often premeditated, experts say.
Attention-deficit hyperactivity disorder, on the other hand, affects a child in all aspects of its life.
So a child letting off steam and running around the house when they come home from school is not a problem in itself.
But if teachers are also reporting they are failing to pay attention in the classroom, and they do not seem to have many friends it may be that they do need a specialist assessment.
Andrea Bilbow. chief executive of the charity ADDISS, (The National Attention Deficit Disorder Information and Support Service), which helps families affected by the condition, says ADHD "is not about a badly-behaved child".
She adds: "It's about a problem in the brain which means a child can't regulate their behaviour or emotion. They don't learn from their mistakes and they can't plan or organise, and they have difficulties with their short-term memory.
"The bad-behaviour label is just used by people who don't have a clue."
Ms Bilbow, who has a child with ADHD herself, said parents are aware there is something wrong from an early age.
"Even when he was at nursery I knew. You hope things will improve, even though you know really that they won't."
Professor Tim Kendall who oversaw the compilation of guidelines on treating ADHD for the National Institute for health and Clinical Excellence (NICE), said: "When parents are saying 'this is getting really difficult and nursery or school is saying the child is difficult to look after, then it's time to get an assessment."
But the arguments around ADHD aren't solely focussed on the diagnosis.
There is also debate about what causes it.
The latest research suggests it is linked, at least in some cases, to a genetic fault.
But even the researcher behind the study say their finding will not explain all cases of ADHD, and that a child's environment also matters.
Peter Hill, an honorary consultant at Great Ormond Street Hospital and ADHD expert, said linking the condition to genetic factors was not new - and was certainly not the whole answer.
"We've known there was a link for the last 20 years. What this study has done is shown what kind of genetic abnormalities might be involved.
"But there are both genetic and environmental causes, and their environmental factors are many."
Professor Kendall agreed genes and environment both played a part and warned it would be wrong to focus solely on genetics.
He warned" It does relieve some people because they think 'it's not my fault - my child was just born like this'.
"The important thing is making sure these kids get really good treatment. If people think it's just a biological problem they will only look for biological solutions - medications."
He said the first option for a child should be to try and help them manage their behaviour and support for them in the classroom. Parents can also learn methods of managing their child's behaviour, such as introducing strict routines.
Only in severe cases should drugs like Ritalin be used, he added.
However, whether or not to use medication is yet another area that causes argument.
Andrea Antunes, whose son takes daily medication for his ADHD, said it had changed his life.
"He's doing well at school. He's also making friends and being invited to parties - which he wasn't before.
"Who am I to deprive him of that?"