I have posted on here several times how worried I get about my son. I go through months where I think he probably does not have adhd and then I notice something and then I start worrying all over again.
Basically, he hardly ever concentrates on anything for that long. He flitters from one toy to another - unless it's something he really likes, like his car. He can concentrate, for example he loves painting pottery and will do that for a reasonable amount of time. However, he is not interested at all in any sort of colouring/painting/ arty stuff and will spend all of 3 mins doing it before he goes to something else.
He also disrupts other children. If they are playing, he will ruin their games. I find this really odd and very annoying!
I know all children are different but I would be interested to know what your 2.5- 3 yr old can do? Or if this sounds at odds with them.