Endogenous Cushing's syndrome in children is a very rare entity. Diagnosis is complex due to the wide variety of tests available. Recently, the utility of salivary cortisol has been proposed for the diagnosis of this entity, although greater evidence is required, especially in pediatric patients. We report a 14-year-old girl with Cushing's disease due to a pituitary microadenoma in whom salivary cortisol determination was very useful for the diagnosis.