ds3 (stepson) has adhd .
At 2 he would not sit still , was very very aggressive , destructive and would not sleep very long.
He was constantly irritating the other children by breaking their stuff. Didnt seem to hear what you would say to him .Even if you asked him to repeat something straight after youd said it he couldnt...it was like he couldnt take anything in. Made trying to teach him anything very very difficult. 
He would ask the same question repeatedly ...once we were going to the park as soon as he was in the car he asked are we at the park yet about 50 times in the space of 10 mins. . If he asked a question and he didnt get the answer he wanted hed just ask the question again over and over until you gave in
Always asking for drinks of juice ....seemed to be addicted to orange squash ( now banned from it rhibena , water or milk only here) , sweets and junk food.
Would also have eating problems ...give him his dinner and hed only eat a couple of forkfulls then say he was full....10 mins later hed want something else (usually weetabix) ...was like he even had no concentration for eating.
Would get minor obsessions , and want somthing yesterday.
Would run until sweat was pouring off him , until his hair was wringing wet .
Had no concept of danger , could not be left alone.
Could not sit still at all. even if he managed to sit down he was constantly figiting.
ONCE he was at school he was medicated , and although the side effect scare the shit out of us , he is better on them. He didnt read until after getting the meds.....just couldnt sit still long enough to learn anything.
He is 10 now. And still a bit haywire , but manageable.
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His reading age is still a bit low , but hes catching up now... thing is hes quite clever so its not a case of hes not intellegent ...just that the adhd blocks the info getting in !.