Development by the Psychological Test Laboratory of the Polish Psychological Association the first fully standardized version of the questionnaire MMPI-2 has opened the possibility of conducting with its use pioneering research in the clinical context in Polish population of patients with neurotic and personality disorders. The conducted research have shown that in the majority of patients eligible for treatment for neurotic and personality disorders in measurement obtained at the beginning of therapy the results indicating neurotic symptoms and disturbance of personality functioning are significantly higher than in the healthy population. Polish version of the MMPI-2 proved to be in this respect a useful tool in the diagnosis of neurotic and personality disorders. As a result of group psychotherapy with elements of individual psychotherapy in most patients profound reduction in the level of neurotic symptoms as well as deep positive change in personality functioning have been observed. Application of the new Polish version of MMPI-2 proved to be useful in monitoring the psychotherapy process of patients suffering from neurotic disorders and personality disorders, which seems to be particularly important from the point of view of planning the follow-up and multi-center research.