This chapter provides an assessment of psychiatric disorders and their development after surgery and the role of personality disorders in hampering surgical success. It explores the question whether or not bad seizure outcome is predicted by pre-existing psychiatric disorders. Concerning postoperative nonepileptic attack disorders (NEADs), there are some reports in the early surveys of the psychiatric effects of epilepsy surgery. Temporal lobe epilepsy itself may be relevant for the impairment of successful personality development. Poor diagnostic differentiation between the psychoses, especially between postictal and interictal ones can have severe consequences for surgical candidates. It was found that all patients with new postoperative psychoses had personality disorders before surgery. As is the case for psychoses, it is also true for affective disorders that the usual psychiatric diagnostic categories do not offer adequate classification for epilepsy patients.