He will for the NHS, and waiting lists are long. Private diagnosis is expensive but if he is diagnosed as having it he can get medication on the NHS if that's what he wants to do.
I have lots of ADD traits (not hyperactivity, which the H stands for). I veer between being very focussed and scatterbrained, I stop and start things to the point where I annoy myself (eg I have numerous half-knitted things on the go), I get easily distracted, which means it can take me ages to do simple tasks (unless I am focussed in which case I am very efficient). There are other things that are typical of people with ADD, such as being unable to do anything before an appointment. I make them for early morning now I realise, as if I have a 2.00pm appointment I can't use the time before it productively at all and the day is wasted. I have no sense of direction, possibly because I don't pay attention, and I create Doom Piles - eg carrier bags filled with assorted items when I 'tidy up', and cupboards that are like junk drawers inside.
I haven't had a diagnosis, as I can't see the point at my age. I've just developed strategies to deal with it, and am kinder to myself than I used to be. I know people who take medication for it, and they swear by it, but they are all younger than me, with jobs and families to juggle.