Well in my case the thing that stands out is that the ADHD diagnosis was given after a very quick/superficial evaluation, whereas the AS diagnosis came after many months of testing, evaluation, and thorough analysis of my developmental history. I cannot exactly speak to whether the two configurations can or cannot coexist in the same person without further study, but my suspicion is that AS and ADHD can appear superficially similar to adults who are observing children and teenagers, merely because of the fact that the child/teenager does not appear to be attending to what the adult wishes they were.