This study was to examine the clinical differences between Stage 0 and normal subjects, using low-dose chest computed tomography (CT) and pulmonary function tests. Enrolled subjects performed as a health check for lung cancer screening including low-dose CT and pulmonary function tests. Subjects were divided into Stage 0, chronic obstructive pulmonary disease according to pulmonary function tests, and normal subjects. The severity of emphysema (visual score) was calculated on three low-dose CT slices. Low-dose CT and pulmonary function tests were performed in 1359 men and 888 women. The numbers and percentages of men and women smokers were 1076 (79.2%), and 107 (12.0%), respectively. A total of 722 individuals had one or more respiratory symptoms, such as cough (69.8%), sputum (75.8%), or shortness of breathing (0.83%). Of the 722 subjects, 71 (9.8%) individuals satisfied the criteria of chronic respiratory symptoms. Among the normal subjects, smoking caused differences in airflow limitation as a result of pulmonary function tests. The proportion of smokers and the visual score were significantly higher in Stage 0 than those in the normal subjects. The percentages of the maximal mid-expiratory flow (%MMF) and of the peak expiratory flow rate were significantly lower in Stage 0 than in the normal subjects. %MMF and the proportion of visual score were significantly lower in the smoking Stage 0 than in the nonsmoking Stage 0 subjects. Smoking would indicate early signs of emphysematous change between Stage 0 and normal subjects in comparison of pulmonary function tests and visual score of low-dose CT.