Attention deficit/hyperactivity disorder (ADHD) is one of the most common psychological disorders of childhood and adolescence, with the three core symptoms inattention, hyperactivity, and impulsivity (Christiansen & Röhrle, 2012). Apart from onset in childhood, diagnostic guidelines require impairment in multiple settings, ie, at home and at school/kindergarten. Thus, assessment of symptoms in those domains is recommended by different guidelines (eg, NICE guidelines [CG072](2008). URL: http://www. nice. org. uk/CG072fullguideline; Deutsche Gesellschaft für Kinder-und Jugendpsychiatrie und Psychotherapie, 2007). Although a diagnosis of ADHD should not be based solely on questionnaires, rating scales such as the Conners’ Rating Scales (CRS) are valuable adjuncts, since they offer parent, teacher, and self-ratings of children susceptible for ADHD (NICE guidelines [CG072](2008). URL: http://www. nice. org. uk/CG072fullguideline). Accordingly, the CRS have been used widely for the assessment of ADHD in different studies (Charach, Chen, Hogg-Johnson, & Schachar, 2009; Deb, Dhaliwal, & Roy, 2008; Green, Wong, Atkins, Taylor, & Feinleib, 1999; Müller et al., 2011a, 2011b). They proved to be especially valuable for the use in large multicenter studies, since they are available in different languages (Müller et al., 2011a, 2011b), and because they assess not only the core ADHD symptoms based on DSM criteria, but also comorbid conditions such as conduct problems and social problems (Conners, 1997). Even though the scales are widely used internationally, cross-cultural comparability has seldom been verified, and culture and language invariance are only presumed (Huss, Iseler, & Lehmkuhl, 2001). The German version of the Conners’ Rating Scale-Revised (CRS-R; Conners, 1997) resulted in different factor models for both the parent (Huss et al., 2001) and the teacher version (Huss et al., 2002). Cross-cultural differences were largest for hyperactivity and impulsivity symptoms in parent ratings (Huss et al., 2001), whereas in teacher ratings those domains produced only marginal differences (Huss et al., 2002). The German inattention scale was almost identical to the American one in both studies (Huss et al., 2001; Huss et al., 2002). Large differences were found for conduct problems in the German CRS-R teacher version (Huss et al., 2002). Thus, cross-cultural differences need to be taken into account when different language versions of the American original are used.

The 3 rd edition of the CRS (Conners 3U+ 00AE; Conners, 2008) was the result of continuous development of the CRS (Conners, 1989) and their revision (CRS-R; Conners, 1997) for children aged 6 (parent and teacher forms) and 8 (self-report forms) to 18 years. According to the author, important refinements include validity assessment, refined T-score cut-off categories, and the assessment of defiance/aggression (Conners, 2008). All Conners 3U+ 00AE content scales (Hyperactivity/Impulsivity, Learning Problems, Executive Functioning, Defiance/Aggression, Peer-/Family-Relations) were deduced with exploratory factor analyses, except for the Inattention scale, which was constructed hypothetically. All symptom scales (ADHD Inattentive, ADHD Hyperactive/Impulsive, CD, ODD) were based theoretically on DSM-IV items. Though the Conners 3U+ 00AE have been in use for 8 years now, hardly any studies report psychometric properties apart from the results published in the test edition itself (Conners, 2008). To our knowledge there are no studies on the various adaptations of the Conners 3U+ 00AE in other languages.