Hi OP, I have a 3.5 year old boy, and a strong suspicion of adhd, due to behavior and family history. for me, the signs are: always, always on the go and energetic even though the average is 3 to 4 hours outside, with tons of bike riding, running around, climbing everything, etc; always needing to touch/twist/pick up/bang everything (no matter how many "no"s), the more tired he is, the more manic he behaves, impulse control (randomg kicking his sister, throwing things, etc) and sensory seeking (always clambering on me, mouthing my arm, pushing, scraping, banging things, likes to be tickled, tacled, hung upside down, have extremes of physical activity-- yells REALLY loudly when there's a lot of noice, as if to be heard over it, notices 'background' noise very easily, in a class of any kind can't sit still or focus on the teacher because too interested in exploring the room, seems to crave attention of any kind--even negative attention is stimulating--and thus acts up if being ignored until attention is focused on him. very little patience or desire for fine motor skill stuff requiring concentration (drawing, puzzles, etc). Very hard to put to bed--says he can't sleep. Can focus intently on stories, videos, but hyperfocuses (eg, tunes everything else out) on these occasions.