Background: The proposal for ICD-11 postulates major changes for posttraumatic stress disorder (PTSD) diagnosis, which needs investigation in different samples. Aims: To investigate differences of PTSD prevalence and diagnostic agreement between ICD-10 and ICD-11, factor structure of proposed ICD-11 PTSD, and diagnostic value of PTSD symptom severity classes. Method: Confirmatory factor analysis and latent profile analysis were used on data of elderly survivors of childhood trauma (>60 years, N=399). Results: PTSD rates differed significantly between ICD-10 (15.0%) and ICD-11 (10.3%, z=2.02, p=0.04). Unlike previous research, a one-factor solution of ICD-11 PTSD had the best fit in this sample. High symptom profiles were associated with PTSD in ICD-11. Conclusions: ICD-11 concentrates on PTSD's core symptoms and furthers clinical utility. Questions remain regarding the tendency of ICD-11 to diagnose mainly cases with severe symptoms and the influence of trauma type and participant age on the factor structure.