To evaluate neuropsychiatric symptoms in PD patients submitted to bilateral deep brain stimulation of the subthalamic nucleus (DBS-STN) by comparison with a control group of PD patients not treated with DBS. 25 consecutive PD patients bilaterally implanted for DBS of STN (DBS group) were compared to a control group of 25 not operated PD patients (CT group) for mood, anxiety and personality traits. The two group were matched for age, sex, duration and severity of the illness. DBS PD patients were assessed three years after surgery. Mood was evaluated through the Beck Depression Inventory (BDI). Anxiety was measured by means of the State-Trait Anxiety Inventory (STAI X1-X2) and personality traits were evaluated with the Structured Clinical Interview for the DSM-IIIR Axis II Disorders (SCID II). Comparing the DBS group and the CT group, no significant differences were found for mood (BDI) or state and trait anxiety scores (STAI X1-X2). Obsessive-compulsive traits scores were found to be significantly lower in the DBS group (p < 0.03). The results of this case-control study suggest that STN DBS does not lead to relevant modifications of mood, anxiety and personality provided that PD patients are well selected for the surgical treatment.