How do you diagnose ADHD versus just a "spirited" child?

[theclick]

We babysit my nephew frequently. We are a close family, so he is used to our house and doesn't behave differently in it versus Grandma's or his own.

He is incredibly active. Won't sit still, can be aggressive (kicks his older brother in the head), Jumps off the sofa, throws frequent tantrums, won't stop talking, and generally will never sit still. There is not one moment in which he does. He also doesn't listen to directions or his name at times. If you tell him to stop something he keeps going. Before we just put it down to being active, but yesterday DH and I both felt it just wasn't right. But when you google ADHD, this seems Normal for a three year old.

Is it normal or will he grow out of it?

I'd be interested to know this too

You need professionals to do quite a lot of tests/watching etc to get a diagnosis.
What you describe could be normal 3 year old behaviour. Quite a lot a very bouncy and have tantrums and have poor impulse control.
How's his sleep?

We never keep him overnight but his mum says he just makes his way into her room multiple times in the night. He does take a while to be put down, around an hour from getting in to bed to sleeping. As soon as he's up he is jumping up and down on the bed.

Very difficult to tell at this age. Most paediatricians will not diagnose ADHD until a child is over the age if six to allow for maturity to kick in etc.

DS was diagnosed aged 8 after being diagnosed with ASD, ...and he was very active as a small child too.

He does sound a bit like it, but like all PPs say often 3 year olds are like this. My DS was like this, he has been diagnosed with ADHD - but only when he was 12. I wish I had got him diagnosed a bit earlier as it would have helped him in school.
However, at age 3 there is no rush so his parents can just keep an eye on him and make sure they do all the things that you would do with an ADHD kid (routine, stay calm , no shouting), and see how it goes. I feel bad because I used to shout at my DS a lot, I didn't realise that this is not the right thing to do. They can educate themselves about it now- there is no downside to that!