Objectives:
The study aimed to determine the severity of trait and state anxiety in patients treated for neurotic and personality disorders with intensive, short-term group psychotherapy and to analyse the change of anxiety intensity in the course of treatment.

Methods:
116 patients (81 females and 35 males) participated in the study. The measurement of anxiety intensity was conducted with the State-Trait Anxiety Inventory (STAI) at the beginning and at the end of treatment.

Results:
The majority of patients (69% of the study group) demonstrated a high intensity of state anxiety at the beginning of the treatment with 47.4% being classified as very high. High intensity of trait anxiety was observed in 64.7% of participants (50.9% –very high). RCI (Reliable Change Index) and RCV (Reliable Change Value) indicated a significant change in state anxiety intensity in 62.1% of participants (48.3% – significant decrease, 13.8% increase). At the end of treatment more than a half of patients manifested medium and low intensity of both trait and state anxiety.

Conclusions:
At the beginning of psychotherapy the majority of patients demonstrated high intensity of both trait and state anxiety. In the course of therapy a considerable reduction of intensity of trait and state anxiety is observed. Significant deterioration in trait anxiety is observed in one out of every thirteen treated patients. Polish adaptation of STAI questionnaire is a useful tool for monitoring effectiveness of psychotherapy and may be successfully applied for screening and detailed diagnosis of neurotic and personality disorders.