I was interested in this subject last night and someone gave me a link to the GAI info for the WISC.

See my un-elegant link: http://www.ksde.org/Portals/0/Special%20Education%20Services/gifted/WISCIVTechReport4.pdf

If you look on pp. 7-9, there are charts that show how often arrangements of GAI/FSIQ scores occurred in sample groups with various issues. AD/HD is one of the sample groups they used. It's probably not that helpful if you don't have scores to work with, but once you get them (or maybe you do have some, I don't know), you'll be able to compare your child's GAI/FSIQ spread with other groups.

So, in our case, we have an 11 point spread. That particular rate occurs at a comparatively significant rate (I made that up) in autism, asperger's, and ad/hd PLUS ld. It occurs more often in ad/hd PLUS ld than it does in just plain ad/hd. Since autism spectrum has been ruled out for my DS6, maybe he has ad/hd PLUS capd instead of one or the other, like I'd been thinking. It's just statistical data and correlation does not equal causation but it's interesting. HTH!