Introduction: Most patients diagnosed with non-small cell lung cancer (NSCLC) die within the first few years after diagnosis. However, only little is known about those who have survived these first years. We aimed to study conditional 5-year relative survival rates for NSCLC patients during long-term follow-up. Methods: All 12,148 patients aged 45 to 74 years diagnosed with stage I-III NSCLC between 1989 and 2008 in the Netherlands were derived from the Netherlands Cancer Registry. Conditional 5-year relative survival was calculated for every additional year survived up to 15 years. Results: Conditional 5-year relative survival rapidly improved with every year survived up to 4 to 5 years after diagnosis. However, a significant excess mortality of 20 to 40% remained. Conditional 5-year relative survival for those aged 45 to 59 years did not exceed 80% for survivors with stage I or II disease and remained just more than 70% for those with stage III disease. For those aged 60 to 74 years, these proportions were 70%, 65%, and 60%, respectively. Conclusions: A significant excess mortality remains in lung cancer after years which may be explained by excess risk of death due to smoking-related comorbidity in these patients. Caregivers should use this information for planning optimal cancer surveillance and informing cancer survivors about their actual prognosis.