It is often assumed that parents completing behavior rating scales during the assessment of attentiondeficit/hyperactivity disorder (ADHD) can deliberately manipulate the outcomes of the assessment. To detect these actions, items designed to detect over-reporting or under-reporting of results are sometimes embedded in such rating scales. This study presents the results of an experimental study in which parents (a) read a scenario telling them that their hypothetical son's teacher has suggested their son may have ADHD and (b) considered assigned goals for the assessment. Parents then completed the accompanying Conners 3Parent Short form (Conners 3-P[S]) in a manner that they believed would achieve their assigned goals. Findings showed that parents are able to engage in deception when completing behavior rating scales. The validity scales embedded in the Conners 3-P(S), however, demonstrated mixed results for detecting parental deception with the Negative Impression validity scale, accurately detecting attempts to malinger in the majority of cases, whereas the Positive Impression validity scale appears to have little to no diagnostic utility for the detection of defensive responding. Clinicians utilizing behavior rating scales should carefully consider results, and nonresults, obtained from embedded validity scales when interpreting parent responses to behavior rating scales as part of an ADHD assessment. C 2015 Wiley Periodicals, Inc.According to the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; American Psychiatric Association [APA], 2013), attention-deficit/hyperactivity disorder (ADHD) describes a disabling condition characterized by excessive and developmentally inappropriate inattention, hyperactivity, and impulsivity. The standard of practice during assessment and diagnosis of ADHD during childhood and adolescence is a multi-method, multi-informant assessment, which may include a developmental history interview with a parent, a physical examination, and rating scales completed by adults that describe ADHD symptoms. In particular, because the diagnosis of ADHD requires that the symptoms of the disorder be present in more than one setting (e.g., home and school), both parents and teachers are often called on to report the frequency and intensity of ADHD symptoms while completing behavior rating scales (APA, 2013;Barkley, 2014).Behavior rating scales can be considered evidence-based assessment tools (Hunsley & Mash, 2007) due to the research supporting their reliability and validity conducted across several decades. Rating scales are far more efficient and less obtrusive to complete than naturalistic observations of child and adolescent behaviors, are relatively inexpensive, and are able to summarize weeks and months of observations of knowledgeable caregivers rating the child or adolescent (American Academy of Pediatrics, 2011;Barkley, 2014;Pelham, Fabiano, & Massetti, 2005; United States Department of Education, 2008). Despite this strong research base and these advantages, behavior rating s...