Does my dog have ADHD or something?

I have a corgi who is hyper. She has a large dog run because she runs away. When I play with her in the yard she gets bored of something within five minutes. It doesn't matter if it's obedience, agility, fetch, etc. She just can't focus on one thing for very long. She stares off into the distance and ignores me. I've tried treats and toys and stuff but it doesn't work.

She is trained. She has done obedience classes and she knows how to do everything. She just has a lack of focus.. She is smart, when she decides to listen.

Try skiping half a meal and use treats. When she is hungry, she will focus better on her obedience tasks. Don't forget to exercise her BEFORE you attempt to train.

Corgis are very high energy dogs who need professional training and a job to do. They also need a lot of exercise. My Corgis get a minimum of an hour+ total walks every day and several hour hikes a few times a week. They often go to a local dog park for a romp as well.

Has she been to professional basic obedience training? Corgis do really well in group obedience - they need to see that other dogs also have to mind. If she has, she needs to go again to a better trainer. Corgis are very intelligent and learn quickly, but the training needs to continue for a lifetime. She is bored and doesn't see you as her pack leader - both very bad from a Corgi stand point. Here are links to professional trainers.
http://www.nadoi.org/index.htm
http://www.apdt.com/

ADD: Then she needs to go to a better trainer. My male Corgi had to repeat Basic Obedience with a more experienced trainer and it has made a world of difference.

You aren't exercising her enough. You need to be walking her every day, in addition to playing with her in the yard.

Start walking her half a mile every day. If she's still acts "A.D.D.", go to a mile or two walks a day. You'll know it's enough when she's excited the whole way through the walk, but dead tired and content when she gets home.

Then she'll chill out and curl up next to you for a nap.

See if Yahoogroups has a corgi list on it, and join it. If not, then do a search on 'breed rescues, corgi'. Contact them and ask for training tips. They'll know all the ins and outs of the breed and can offer you some solid information.

Get some roller blades and take her for a 'walk' using those... or ride a bicycle (they make special bars for leash attachment)

No, you just aren't in control of her. Try training.

she might be a inbred dog