Background: Three decades of research on disturbed grief has led to the inclusion of persistent complex bereavement disorder (PCBD) in DSM-5 and prolonged grief disorder in ICD-11. For clinical practice and research, it is important that PCBD and PGD represent the same construct. Objective: We conducted three studies, the goal of which was to evaluate differences and overlap between criteria for PCRS and PGD. Method: The first was a cross-sectional study with over 400 bereaved people. The second was a longitudinal study including 500 individuals. The third evaluated PCBD and PGD among 8–18-year-olds. Results: Outcomes of the studies indicated that (i) PCBD encompasses three distinguishable symptom-clusters and PGD one cluster, (ii) both syn...