||In this study, we tested the validity of a dissociative subtype in a sample of 225 detained adolescents (142 boys, 83 girls) likely meeting full or partial criteria for posttraumatic stress disorder (PTSD). Competing theories of dissociation pose controversy regarding dissociation as a taxon versus a continuum, and results of the current study contribute to this debate by providing evidence of distinct group differences between those high and low in dissociation. Mixture modeling revealed 2 groups of youth with differing levels of depersonalization/derealization dissociative symptoms. Differences between the 2 groups of youth were investigated regarding trauma exposure and several posttraumatic reactions: posttraumatic stress symptoms (PTSS), emotion dysregulation, and emotional numbing. Compared with youth classified in the low-dissociation group, youth who exhibited high levels of dissociation demonstrated higher levels of total PTSS, posttraumatic symptom clusters of emotional numbing, intrusion, and associated features, as well as reporting more difficulties with emotion dysregulation. To test theory regarding the factors that increase the likelihood of persistent dissociation, bootstrapped regression analyses were performed to examine the possibility of an indirect effect of peritraumatic dissociation. Results consistent with statistical mediation suggested that the presence of peritraumatic dissociation at the time of trauma may contribute to the continuation of dissociative symptoms as a more generalized pattern. The results of the current study have implications for clinical treatment with traumatized youth.