In order to evaluate the severity of behavioral complications after deep brain stimulation of the subthalamic nucleus (STN-DBS) for Parkinson's disease and to explore possible predictive factors, the authors evaluated 22 patients for pre- and postoperative symptoms using a neurobehavioral battery. Compared to the time before STN-DBS, several behavioral symptoms had worsened in terms of prevalence and severity and appeared de novo in other patients. Apathy, anxiety, and suicidal ideation increased significantly, while depressive symptoms appeared stable. Compared with patients who improved, patients who had deteriorated behaviorally had similar prevalence and severity of preoperative behavioral symptoms but significantly shorter disease duration.