This study will evaluate the efficacy and safety of Tarceva in two groups of patients with non-small cell lung cancer who have not been pre-treated with chemotherapy. One group, consisting of patients who have never smoked, will receive Tarceva 150 mg/day, and the other group, consisting of current/former smokers, will receive Tarceva 150 mg/day increasing to a maximum of 300 mg/day. The anticipated time on study treatment is 1-2 years.