Correlation between passive smoking and nasal mucociliary clearance (MCC) in pediatric population has not been reported before. Therefore, in this study, we aimed to investigate the relationship between environmental tobacco smoke and nasal MCC in children whose parents smoke in or outside the house. Three groups of subjects were evaluated: control group (group 1) with 18 children who were not exposed to environmental smoke, 15 passive smokers living with at least one adult household member smoking outside the house (group 2), 17 passive smokers living with at least one adult household member smoking inside the house (group 3). Parents of children were asked to answer our questions regarding their smoking history, and nasal MCC time was assessed for all individuals of the 3 groups. The mean MCC value in control group, group 2 and group 3 were 7.33 +/- A 2.91, 10.00 +/- A 4.78 and 12.41 +/- A 3.44, respectively. Differences between the mean nasal MCC values of the groups were statistically significant (p < 0.01). The comparison of MCC values between control group and group 2 did not reveal significant difference, but since p value was very close to significance level, in larger series it could be significant. (p = 0.067). Also, when we compared the MCC values between group 2 and group 3, there was no significant difference (p = 0.173). But, the difference between MCC values of control group and group 3 was statistically significant (p < 0.001). Parental smoking both inside or outside the house seemed to increase nasal mucociliary clearance time when they are compared with healthy controls. Further studies with larger study groups also measuring direct quantitative doses of smoking are needed to verify this important issue.