Although substantial evidence suggests altered executive functioning and autobiographical memory in posttraumatic stress disorder (PTSD), the clinical significance of these findings remains unclear. Here, we investigated the effects of cognitive-behavioral therapy (CBT) on different aspects of cognitive functioning (working memory, interference susceptibility, conflict adaptation, autobiographical memory) in PTSD patients in a pre-post control group design with a nested cross-sectional element. Cross-sectional analyses at baseline were conducted on 58 PTSD patients, 39 traumatized (TC), and 45 non-traumatized controls (NTC). Intervention effects were investigated before and after 25 CBT sessions in 25 PTSD and 34 untreated NTC individuals assessed in parallel. At baseline, PTSD patients showed higher conflict adaptation than the NTC group and less autobiographical memory specificity than both control groups, suggesting particularly the latter to be a correlate of PTSD. No consistent evidence for treatment-induced improvements in cognitive functioning emerged on the group level or from associations between intra-individual clinical and cognitive changes. Analyses on the role of cognitive functioning on subsequent treatment effects revealed a predictive effect of backward digit span on CBT-induced reductions of depressiveness, but no other significant effects. Our findings highlight the need for further research to identify more relevant predictors of differential treatment response.