We investigated the validity of theory driven profile interpretation of the MMPI (Hathaway & McKinley, 1943) Dutch Short Form (DSFM; Eurelings-Bontekoe, Onnink, Williams, & Snellen, 2008) as a measure of personality organization (PO) in a naturalistic follow-up study among 576 psychiatric outpatients receiving brief cognitive behavioral group therapy. Results showed that this assessment method was useful in predicting dropout as well as treatment response. Patients with a latent psychotic PO profile and a manifest low-level borderline organization profile were 3 times more likely to drop out than patients with other PO profiles. Patients with a latent psychotic PO profile who continued treatment had deteriorated at 4-month follow-up. Patients with a manifest low-level borderline PO profile who remained in treatment, however, showed considerable therapeutic progress. We conclude that theory driven profile interpretation of the DSFM as an assessment of PO may be useful in predicting dropout and treatment response to cognitive behavioral treatment of Axis I disorders.