Unlabelled: The assessment of defense mechanisms in psychotherapy is currently one of the most used ways to evaluate the effectiveness of psychotherapy. In literature there are few reports on defense mechanisms changes by short-term treatments., Aim: To determine whether the defense mechanisms are changed after twelve sessions of short-term psychotherapy related to psychopathological symptoms, severity and overall functioning., Methods: Twenty patients (12 F and 8 M; age 38.4) affected by anxiety and mood disorders were recruited to the study between November 2008 and July 2009 and were assessed with the Defense Style Questionnaire-88 (DSQ-88), scale Symptom Checklist-90-Revised (SCL-90-R), scale Clinical Global Impression (CGI) and scale Valutazione Globale del Funzionamento (VGF) at the beginning and after short-term psychotherapy. Half the sample also assumed drugs. The treatment was supportive-expressive psychotherapy of Luborsky, a short focal dynamic therapy, characterized by the integration of supportive and expressive techniques., Results: Both patients showed a significant decrease in immature defenses and a significant-increase in mature defenses (p < 0.01). Mature defenses were significantly correlated with severity (r = -0632; p = 0.003) and overall functioning (r = 0529; p = 0.01)., Discussion: Immature and mature defenses seem to be a useful outcome measure in short-term psychotherapy as well as severity and overall functioning and the combined treatment may be most effective in reducing immature defenses.