Objective: Although existing instruments contain items addressing the effect of ADHD medications on emotional expression, a review of measures did not yield any instruments that thoroughly evaluated positive and negative aspects of emotional expression. Method: The Expression and Emotion Scale for Children (EESC), a parent-report measure, was developed from an analysis of qualitative data from parent focus groups and expert opinion. Data from 179 parents and children treated with stimulants or atomoxetine are used to examine the psychometric properties of the EESC. Results: The EESC demonstrates good internal consistency and test-retest reliability. A factor analysis yields three factors (positive, flat, and emotional lability) that were consistent with the predicted structure of the measure. Small to moderate correlations between the EESC and psychological symptom measures are found, with the strength of the relationships varying by symptom measure. Conclusion: The EESC shows appropriate psychometric properties and is appropriate for use in clinical and research settings. (Contains 6 tables.)