COPD  

Depending on your condition and other underlying conditions, you might (likely) need a Special.  Likely mitigation is a Pulmonary Function Test once or twice a year (they'll tell you) and if the results meet certain parameters, you'll be ok.  You will need a letter from your treating physician saying he thinks you can fly.

You need a real AME, not a guy that does it as a hobby.  They will know what paperwork/treatment you need, what paperwork to send in.  And the real good ones know who to call at OKC to move your paperwork along.

If it is managed and under control, absolutely you can fly. I did it for years.