BACKGROUND: Carcinoembryonic antigen (CEA), a serological marker of malignant tumors, may show a modest increase under some nonmalignant conditions, such as aging and cigarette smoking. OBJECTIVE: We analyzed clinical characteristics according to smoking status and determined whether serum CEA levels are associated with pulmonary function. Method: The cross-sectional data from 2,691 subjects who participated in health screening programs were analyzed. The subjects were divided into 3 categories according to smoking status: never-smokers, former smokers and current smokers. A systematic method to derive an optimal cutoff point of CEA which indicates the difference in FEV1% was used. RESULT: Smoking status was associated with increased serum CEA levels, WBC counts and neutrophil counts and decreased FEV1% in never-smokers, former smokers and current smokers with increasing correlation. Logistic regression analysis adjusted for age and sex showed no differences in FEV1%, WBC counts and neutrophil counts between never-smokers and former smokers. Logistic regression analysis adjusted for age, sex, BMI and smoking amount in former and current smokers showed significant differences in FEV1, WBC counts and neutrophil counts between those with a CEA level of <2.0 and those with a CEA level of > or =2.0. CONCLUSION: Our results suggest that smoking cessation may affect recovery of systemic inflammation and decreased lung function. A slight elevation in serum CEA in former or current smokers may be associated with systemic inflammation and decreased pulmonary function.