Hi Bob ... Welcome! YES on all counts. When they test children at a very young age, not everything is always 'present' or at the forefront ... and as they grow and develop, other things can develop or come to light, so it is very possible that he can have 'more' than the ADHD (as if that isn't enough) going on. And ODD and ADHD often travel together. In the case of my DS, he was diagnosed with ODD-alone when he was about 5 ... when he was 9, we had a full evaluation done which showed he also had ADHD and CAPD ... the ADHD was a surprise to us all (he's not the hyperactive type, his ADHD is more the impulsivity kind and definitely works with the ODD.)
ODD, by itself, generally isn't medically treated. The best way to work with such a child is behavior mods (although some ADHD meds help ... which is what we found with our DS; when they put him on Concerta for the ADHD, the ODD behaviors subsided.) Understanding that these kids are not being intentionally difficult and defiant is key ... If you look on our Resource Site (above) you'll find a lot of info on ODD, 2 in particular will help. The first is the Book Review Section ... knowledge is power, and the more you understand this disorder, the better able you will be to deal with this and help your child. (My favorite book is "Winning Cooperation ..." by Kenneth Wenning, although Ross Greene's "The Explosive Child" is probably the most popular.) The other section is the Sample Behavior Chart. Your DS is at the perfect age for this to be a very effective tool to help change his behavior (as well as the tone in the house.)
Anyway, I would suggest that you have a re-evaluation done. A child of 6 is very different than at 3, and things do change. However, you don't need a diagnosis to start dealing with ODD right away. If he meets all the criteria, you really don't need a doc to confirm (or deny) it. Since it's not really a matter of meds, but of behavior mods, you can do this on your own.
Good luck.
Please come by often. What I found most helpful in all of this is knowing I was not alone ... having other parents in the same boat who understood what it was like to live my live, to have a child like this ... this board has saved my sanity over the years!
Nancy
