Ok, sorry, seem to have generated confusion and didn't mean to. You can definately get DLA if you have ADHD, sorry for any confusion, no question at all-
BUT for any DLA decision they will look not just at whether there is a disability but how it affects your life, specifically if you need care/help to get around.
When deciding whether and how much to award, they will not take into account anything which they see as soly a behavioural problems.
Now this sometimes affects ADHD cases and mean either no award is given or that it is low. For example, a boy who was running around setting fire to the big dustbins in town, had an ADHD dx. No DLA awarded because decision maker saw it as behavioural.
I think this is crap btw because IME behavioural problems are often evidence of an undiagnosed mental health problem anyway, but this is honestly what the law says.
Now I'm not saying it always happens and actually I don't know what conduct disorder is, but just from the name, I think its just the sort of thing which might encounter this problem. The appeals process can take 4 or 5 months to go through, plus its not a nice experience, really, and I wanted to advise the op to take steps to avoid having to go to appeal. Its just a case really of phrasing the form to stress the mental health side rather than the behavioral side, really.