People with ADHD and dyslexics are often slow readers. However, dyslexia should only affect reading (although new studies say it might affect word recall and memory) and ADHD should appear in other parts of life, often with impairments in executive functions.
If you've ever seen letters flip as you read, that's probably dyslexia. Other things dyslexics do include inserting words from a line lower into the current line, having a bad grasp of phonics, and rereading or skipping lines.
For more information on dyslexia, a good book is The Dyslexic Advantage.