This article explores the questions surrounding the actual differences between PTSD and complex PTSD. Complex Post-Traumatic Stress Disorder/CPTSD appeared in 2019 in the ICD-11. All diagnostic requirements for PTSD are met associated with problems in affect regulation and difficulties in sustaining relationships. Complex diseases should recognise and differentiate overlap syndromes as distinct entities. But it is possible that the ‘complex’ may lead to a loss of understanding and potential for action. Moreover, the specific symptoms of affect regulation, negative self-concept and disturbances in relationships of CPTSD seem to be included in the APA's PTSD. The treatment of CPTSD also appears to be ‘complex’. Some authors emphasise the importance of introducing the CPTSD, but others criticise recent attempts to reconceptualise certain cases of borderline personality disorder. Moreover, to date, there is no clear pathophysiological evidence supporting a distinction between PTSD and complex PTSD. This is an invitation to return to meticulous clinical observations.