Abstract Posttraumatic Stress Disorder (PTSD) and Complex PTSD (C-PTSD) represent two clinically distinct responses to traumatic experience. Although they share some symptomatological features, they differ substantially in etiology, clinical presentation, impact on global functioning, and therapeutic implications. This article examines the theoretical and empirical foundations of this distinction, with reference to the major international nosographic systems (ICD-11, DSM-5-TR