BACKGROUND Although post-traumatic stress disorder and obsessive-compulsive disorder have distinct diagnostic criteria, some psychopathological phenomena seem to be shared, which may lead to misdiagnosis and erroneous treatment decisions. This scoping review explores the psychopathological similarities and differences between these two disorders. METHODS The review complies with the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and included articles published in Portuguese, English, or Spanish in the last 50 years indexed in the PubMed database. Case-reports were excluded. RESULTS Fifty-three studies with different designs were included (30 [56.5%] were cross-sectional studies; eight [15.1%] were case-control studies; one [1.9%] was a cohort study; three [5.7%] were clinical trials; nine [17%] were reviews/systematic reviews; and two [3.8%] were meta-analyses). The main psychopathological aspects described by the studies included were flashbacks x obsessions; avoidant behavior (AB); depressive, anxious, and somatic symptoms; sexuality, sleep, and appetite; psychiatric comorbidities; and suicidality. The intersection between clinical features seems to occur in the extrinsic psychopathological dimension. CONCLUSIONS The disorders' core psychopathological symptoms (intrinsic characteristics) are distinctly different, since flashbacks and obsessions are consequences of different predominant defective mental functions: the former derives from defective memory, the latter from defective thought. Along the same lines, the ABs observed in the two disorders are products of different purposes and inner necessities.