I've been on paleo for 9 months now. And I was also diagnosed with ADD. I thought it would get better on the paleo diet, but it has gotten worse. At least, I find it very difficult to focus on work, but rather read books & sites about food ;) It's good, but not in a healthy way.. I'm quite strict by the way with food, so no gluten or dairy, almost no sugar, easy on fruits.
I haven't found out why, but some days it it worse than others. I got advised to get on meds, but I refused and will partake in courses that will help me focus and get my short term memory better.
A few months ago, a Dutch scientist did a PhD on ADHD & diet, and got great results: http://www.naturalnews.com/031386_elimination_diet_ADHD.html It was a strict diet with only rice, fruit, white meat, vegetables & water. 78% of the patients improved significantly. She then re-introduces foods one by one over a long period of time, to find out which foods cause the symptoms. It might be sugar, it might be fish, it might be eggs, or grains, you will only find out when you test it.
This let me to believe there is still some more room to experiment and kick out foods. I'm gonna keep a diary and write down every single food & also how I experienced my ADD. This will (hopefully) show which foods seem to worsen ADD. It might take a lot of months! I skipped to (almost) fully organic vegetables too lately, instead of regular; maybe that also helps, I don't know yet.
Or else, I just have to live with it, meditate often, force myself not open 20 tabs and read everything for 1 minuten and skip to the other... :)