The aim of our study was the comparative evaluation of a relative survival model and a Cox model to determine the prognostic factors of survival for patients with surgically cured non-small cell lung cancer (NSCLC). We focused particularly on the exact role of age in this survival. 156 patients treated between 1975 and 1988 were studied. Both univariate and multivariate analyses were performed, using the actuarial method and the Cox model for crude survival and the Hakulinen model for relative survival. This study confirmed the poor prognosis of NSCLC, even if a curative surgical procedure has been possible, with a 5-year survival of 48% for stage I tumours but only 6% for stage III tumours. The most significant prognostic factor was the postsurgical TNM staging. The relative survival method of Hakulinen dismissed age as a significant prognostic factor. Our study underlines the usefulness of relative survival methods which should be more frequently employed to allow comparisons between series of different origin and to set up multicentre therapeutic trials.