Background: Surfactant protein D (SP D) is crucial in controlling the immunological response of the peripheral airways, Surfactant changes caused by airway inflammation may have a role in the pathophysiology of asthma. Aim of this study: was to assess the value of salivary SP D in Preschool asthmatic children. Methods: in our case control study including 30 non-asthmatic controls and 30 preschool asthmatic children aged 2-5 years old, we assessed salivary SP D and pulmonary functions using impulse oscillometry (IOS) then the correlations between salivary SP D levels and IOS indices were analyzed.Results: Salivary SP D levels were increased in asthmatic group with mean ± SD of 32.52±12.88 pg/ml compared to 5.98±2.87 pg/ml in healthy controls. Moreover, it was correlated with poor pulmonary functions using IOS indices with cutoff expression value of SP D >8.19 using ROC curve at the optimal sensitivity 83.3% and specificity 81.0% to differentiate asthmatic children from controls. Conclusion: Salivary SP D can be a useful marker for childhood asthma and can monitor deterioration in pulmonary functions in preschool asthmatic children