Hi, I'm in my 40s. One of the tools my PNP used to assess me for ADHD last year was the CAARS (Conners Adult ADHD Rating Scales):
http://www.pearsonassessments.com/caars.aspx

I also used the online tests by Amen (recommended by my PNP), which I thought were pretty good, as they break the diagnosis down into a number of ADHD subtypes and there are questions that help with differential diagnosis (from depression, anxiety, etc.). I think I paid about $10 to take these.
http://www.amenclinics.com/my-brain-...st-your-brain/
Just beware at this site, there are many opportunities to buy books, vitamins, etc. But I thought their test was very comprehensive and didn't feel like I do on so many tests--that their questions are "one size fits all."