You read on the net that "a cough that won't go away" is an early symptom of lung cancer. My question is... "How long should the coughing persist before it should be taken seriously?" 3 months? 6 months? I started with a cough 4 weeks ago, and I still have it. It could be a chest cold or very slight pneumonia, so I do not want to rush to conclusions or jump the gun here. I was just wondering what that duration of coughing might be that would trigger a cause for concern. Thanks.