Objective: To summarize the literature investigating changes in emotional expression (EE) as a function of pharmacotherapy in the treatment of ADHD and to differentiate emotional effects related to ADHD pharmacotherapy from emotional effects related to ADHD as a disorder. Method: English language articles published from January 1, 1988, through August 31, 2008 were identified through a PubMed literature search using the search terms "attention," "ADHD," "hyperactive," "hyperkinesis," and "ADD" cross-referenced with medication terms "amphetamine," "lisdexamfetamine," "methylphenidate," "guanfacine," "atomoxetine," and "clonidine." The search was limited to randomized, controlled trials. Abstracts from all identified articles were selected for further review if they met criteria including (a) presence of a placebo arm, (b) children less than or equal to 18 years of age, (c) greater than or equal to 20 participants, and (b) study design elements that would allow reviewers to determine whether EE phenomena were specifically attributable to medication effects versus alternative explanations (e.g., time, maturation, baseline comorbidity, selection artifacts, or treatments other than the medication-placebo contrast). Qualifying full-text articles were reviewed for prespecified EE terms. Results: Of 148 articles that met selection criteria, 47 reported varying types of EE. Eight of these included two active treatment arms. Hence, 55 data sets were identified. Patterns of change in EE in studies meeting search criteria are discussed. Data sets that reported accounts of EE by the percentage of patients were compiled and further analyzed for specific medication classes. The changes in EE are further discussed as (a) salutary or detrimental, (b) associated with time of day or circumscribed, and (c) presumed to be caused by pharmacological effects. Conclusions: Definitive methodologies for assessing the presence of changes in EE in clinical trials and guidelines for the evaluation of EE in clinical practice are yet to be established and are needed. Such guidelines could be used by clinicians to monitor positive and negative changes in emotion when patients are taking medications for their ADHD. (Contains 5 tables.)