Yes, 100%

An adult will get just as many benefits from counseling and other therapies (primarily medication) as a child would.

Note that an ADHD diagnosis in adulthood usually comes with a shocking assortment of emotions as the adult suddenly realizes how ADHD played an unknown role in their childhood and earlier adulthood.

Some emotions are friendly: like relief in discovering that they aren’t and weren’t lazy or stupid.

Some are tough: like anger at parents and teachers who may have disciplined or guided them in ways that were unproductive.

Some are complicated: like wondering about whether to change a career that they’d been committed to for years (maybe decades) but that never felt “right” for them.

It’s big work to negotiate these emotions. A newly diagnosed adult may have more counseling challenges than a child, because the adult has two things to reckon with: (1) ADHD in the present and (2) ADHD in the past.

Here’s a good intro article for on next steps for an adult just diagnosed with ADHD. https://www.additudemag.com/forums/topic/just-been-diagnosed-is-addictiveness-a-factor/

————I wrote this post in reply to a question on Quora.

See here for more answers: 
https://www.quora.com/Can-an-adult-who-had-not-received-an-ADD-ADHD-diagnosis-as-a-child-be-tested-for-this-in-adulthood-and-benefit-from-counseling-and-other-therapies