<em>DSM-5em> and <em>ICD-11em> criteria for posttraumatic stress disorder (PTSD) differ substantially.
<em>ICD-11em> proponents argue that the proposed criteria will reduce diagnostic comorbidity.
We examined differences in PTSD prevalence and comorbidity between <em>DSM-5em> and <em>ICD-11.em>
<em>ICD-11em> yielded comparable comorbidity rates but PTSD prevalence 10–30% lower than <em>DSM-5em>.
<em>ICD-11em> does not improve specificity and may miss individuals with clinically significant PTSD.