Earlier diagnosis of lung cancer improves outcomes for two main reasons. First, the disease stage may be earlier allowing more chance of curative-intent treatment. Second, patients may be fitter at presentation. Functional status is one of the most important independent predictors of survival. Lung cancer is caused by smoking in 80-85% of cases. Patients who do not have smoking-attributable lung cancer are often diagnosed late. So it is important to refer patients who have persistent symptoms either for chest X-ray, or when symptoms persist and no alternative diagnosis is found, refer for consideration of CT.