75 adolescent psychiatric patients were diagnosed with the perceptual projective test the Defense Mechanism Test (DMT) and also according to Kernberg's theory of personality organization (PO). The test protocols were scored in respect of 130 DMT variables and analyzed by means of partial least squares (PLS) discriminant analysis. The objective was to try to separate the three types of PO, psychotic (PPO), borderline (BPO) and neurotic (NPO) by means of the DMT and also to compare the results with a similar study in adult psychiatric patients. The results showed that it is possible to separate significantly the three groups of PO. The BPO group seemed to be heterogeneous. The results were fairly similar to those obtained with adult psychiatric patients. The overall results supported the concurrent validity of Kernberg's theory of PO and for the DMT as well. The DMT seems to be a useful diagnostic method in respect of adolescent psychiatric patients.