Abstract: Objective: To assess the effect of computed tomographic (CT) section thickness, CT enhancement on stage I non-small cell lung cancer (NSCLC) measurements calculated with three-dimensional methods. Methods: 92 patients of the stage I NSCLC were analyzed on CT scan with 2 mm, 7 mm CT section thickness; of which 76 had 7 mm CT section thickness enhanced scanning. The data were sent to the CT post-processing workstation, the lesions were automatically delineated by using computer-aided diagnostic software. The maximum diameter: d (ram), volume: V (mm³), mass: m (g) of the lesions were measured on each section thickness, before and after enhancement. Means and variances were calculated, and the differences across the two section thicknesses, before and after enhancement were studied by using pair T-test. Results: Differences in the means of d, V, m were significant between a section thickness of 2 and 7 mm (P ＜ 0.05); Differences in the means of d, V were not significant between 7 mm plain CT and contrast enhancement (P ＞ 0.05), while differences in the means of m were significant (P ＜ 0.05). Conclusion: Section thickness of 2 and 7 mm selection on chest CT scan had a certain influence on maximum diameter, volume and mass measurement result of stage I NSCLC; CT enhancement could affect measurement result of mass.