Hearing Aids and Headphones Can a hearing aid wearer use headphones?
No its not a good idea but it depends on the needs:
1. Listening to Music or
2. In some sort of Call Center - where you are taking phone calls all day.
1st Hearing Aids and Headphones or headsets and music there are two possible solutions:
A. The solution today is with the new wireless hearing aids, you can connect your Bluetooth iPod or iPhone directly to your hearing aid with no wires. This lets you listen to music through your hearing aids, just as if they were headphones themselves. And the best part is, you’re already wearing your hearing aids so all you have to do is push play.
B. Or you if your hearing aids have a telecoil, you can get something like the Quattro 4.0 Adaptive Bluetooth System. You can Connect and stream your cell phone, your television, stereo for music...up to five other devices to your Quattro 4.0 Adaptive Bluetooth Listening System for a pretty good listening experience.

2nd, Hearing Aids and Headphones in a Call Center. This is more for folks that are working, go into a job and are required to take calls, with headphones - headsets. Afraid to say, The majority of over the ear headphones will create feedback (distorted sounds) with behind the ear hearing aids - and they will almost certainly be uncomfortable. And in the ear headphones you will have to take the hearing aids out - taking a chance to lose them..because the too will most likely create feedback.
The really only solution, to minimize feedback is to take the hearing aid out...or test the for the pilot headphones.

Private pilots, wear these large headsets. That cover the ear and more...not really pressing on any part of the hearing aid...if you wear the headset and the hearing aid has a t coil in it, then all the signals - between tower and pilot, will be broadcast right through the hearing aids. Its amazing and it works quite well.