The purpose of this study was to investigate the affect, as measured by “Positive and Negative Affect Schedule” (PANAS), its influence on psychopathology, and to examine the effect of changing affect during cognitive behavioral therapy (CBT). The study was carried out at the psychotherapy training center, Karlstad University. The hypothesis was whether clients with mental disorders have a self‐destructive affective personality (low PA and high NA) and healthy individuals have a self‐actualizing personality (high PA and low NA). Thirty‐two healthy participants and 44 clients participated in the study. The clients were asked to fill in the PANAS once throughout CBT, either during evaluation, treatment or finishing phase, accordingly there were three different groups at different therapy phases. The healthy subjects were also asked to fill in the self‐report scale once. The comparison of the three phases of therapy and the four affective personality types showed a significant difference between the phases of therapy and the four affective personality types: totally 16 (of 22) and eight (of nine) clients measured at the evaluation and treatment phases, respectively, had a self‐destructive personality. However, at the end of therapy five (of 13) clients had a self‐actualizing personality characteristics, while only three of them were self‐destructive. Furthermore, the results indicate that affective personality does not seem to be a basic and stable personality trait, which could be altered by therapy. The affections measured by PANAS may be influenced by psychopathology and CBT, when conducted by candidate therapists it can be effective in terms of affect changes.