Background: DSM-5 Reactive Attachment Disorder (RAD) and Disinhibited Social Engagement Disorder (DSED) are rare, understudied, and controversial disorders. Methods: Comorbidity in children diagnosed with RAD or DSED was compared with comorbidity in ADHD and autism to determine if RAD/DSED comorbidity differed from that for the two most common disorders in child psychiatric clinics. Samples included 4-17-year-olds, 20 with RAD and/or DSED, 933 with autism, and 895 with ADHD. Children with RAD/DSED were removed from their neglectful environments at a mean of 4 years and were a mean 10 years when studied. Mothers rated the children on the Pediatric Behavior Scale assessing oppositional behavior, conduct problems, ADHD, anxiety, depression, and other symptoms. Results: Five of the 20 children with RAD/DSED had DSED without RAD, 15 had RAD with DSED, and none had RAD without DSED. All children with RAD had callous-unemotional traits (CU) and 73% had conduct disorder (CD). No children with DSED-no RAD had CU or CD. Children with RAD + DSED were considerably more impaired than children with DSED-no RAD, autism, and ADHD. Conclusions: Findings are consistent with other studies indicating high CD/CU comorbidity in RAD and extreme rarity of RAD without DSED, findings which are not noted in the DSM-5. (C) 2017 Elsevier Ltd. All.rights reserved.