An abnormal chest x-ray is one, but not the only indication of CF. I am 18 with CF and I have had clear lungs before. I don't mean to say that to scare you, you could have it or you could be ok. There are other possible indications. Some are: 1. Does your skin taste salty? Or if you have a spouse, do they think you have a salty kiss? 2. Look at the tip of your fingers, do they curve out and get wider from the cuticle of your nail to the tip of your finger? 3. Do you have a heavy cough or cough up spudum often and if you do is it really thick? These are just a few signs but not definite answers to rather you have CF or not. You could have something else similar. Plus, your just looking into the lungs. Do you have often stomach aches after you eat or abnormal stool? These could be indications but the true indication is the answer from a CF EXPERIENCED DOCTOR!!! It is important to know that not every doctor can discover CF or even know anything about CF. I have gone to alot of doctors with a cough that are not CF doctors and they say I just have bronchitis. However, after I tell them about CF, I have to explain to them what it could be instead of the other way around!! If you think you could have it, don't just ignore this! Call a CF Medical Center and ask questions. If they feel you should come in and get tested, do it! If you do have it and put off treatment, it will only make it worse for you in the long run. And, if it isn't CF and something else, that too could need immediate treatment.