Background: There is ongoing debate as to whether emotion regulation problems should be improved first in order to profit from trauma-focused treatment, or will diminish after successful trauma processing. Objective: To enhance our understanding about the importance of emotion regulation difficulties in relation to treatment outcomes of trauma-focused therapy of adult patients with severe PTSD, whereby we made a distinction between people who reported sexual abuse before the age of 12, those who were 12 years or older at the onset of the abuse, individuals who met the criteria for the dissociative subtype of PTSD, and those who did not. Methods: Sixty-two patients with severe PTSD were treated using an intensive eight-day treatment programme, combining two first-line trauma-focused treatments for PTSD (i.e. prolonged exposure and EMDR therapy) without preceding interventions that targeted emotion regulation difficulties. PTSD symptom scores (CAPS-5) and emotion regulation difficulties (DERS) were assessed at pre-treatment, post-treatment, and six month follow-up. Results: PTSD severity and emotion regulation difficulties significantly decreased following trauma-focused treatment. While PTSD severity scores significantly increased from posttreatment until six month follow-up, emotion regulation difficulties did not. Treatment response and relapse was not predicted by emotion-regulation difficulties. Survivors of childhood sexual abuse before the age of 12 and those who were sexually abused later in life improved equally well with regard to emotion regulation difficulties. Individuals who fulfilled criteria of the dissociative subtype of PTSD showed a similar decrease on emotion regulation difficulties during treatment than those who did not. Conclusion: The results support the notion that the severity of emotion regulation difficulties is not associated with worse trauma-focused treatment outcomes for PTSD nor with relapse after completing treatment. Further, emotion regulation difficulties improved after trauma-focused treatment, even for individuals who had been exposed to early childhood sexual trauma and individuals with dissociative subtype.