ADHD and autism are separate diagnoses with separate criteria, but they co-occur more often than was historically recognised, and some traits, such as difficulty with attention, sensory sensitivity, or social communication differences, can look similar on the surface while having a different underlying cause.
Why differentiation matters
Getting the right diagnosis, or the right combination of diagnoses, matters because the support and, where relevant, treatment options differ. A clinician experienced in both conditions will look at the pattern, timing and context of traits, not just whether a trait is present, to understand what is driving them. This is why a thorough assessment takes time and structured tools, rather than a short questionnaire alone.
Living with both
Many people are diagnosed with both ADHD and autism, sometimes called AuDHD informally, and describe the combination as creating its own distinct pattern of strengths and challenges, rather than simply the sum of two separate conditions. A good assessment report should reflect that individual pattern rather than applying a generic template.