Reactive Attachment Disorder (RAD) remains one of the least evidence-based areas of DSM and ICD nosology. Recent evidence from severely deprived institutional samples has informed review of RAD criteria for DSM-V; however, this data is not necessarily generalizable to expectable child environments in the developed world. We provide the first systematic study of this important syndrome in maltreated non-institutionalized adolescents from a high-income country. 153 high-risk adolescents in English out-of-home Looked After Care (LAC: mean age 174 months, SD 23, 52 % male) and 42 low-risk (LR) community controls (mean age 168 months, SD 18, 38 % male) were assessed for RAD behaviors. Data on maltreatment and care history were collected from social work reports and concurrent psychopathology from caregiver report. Triangulated data sources informed independent researcher ratings of adaptive functioning. LAC adolescents showed high prevalence of RAD behaviors. Factor analysis showed four symptom groups; Disinhibited Indiscriminate, Attention Seeking, Superficial Relationships and Unpredictability. RAD was associated with multiple maltreatment experience, earlier entry to care and increased rates of psychopathology. Superficial Relationships and Attention Seeking factors showed strong independent association with particularly pervasive functional impairment. Disinhibited RAD behaviors are identifiable with high prevalence in non-institutionalized high-risk adolescents. They are strongly associated with psychopathology and functional impairment. Retention of this subtype in DSM-V is supported. Findings on the inhibited subtype in adolescence are less persuasive. RAD behavior is a relevant marker of developmental impairment, has significant clinical implications and is deserving of further study within non-institutionalized risk populations.