We assessed the concurrent validity of the Hospital Anxiety and Depression Scale (HADS) and the Geriatric Depression Scale (GDS) against the Hamilton Rating Scale for Depression (Ham-D) in patients with Parkinson's disease (PD). Forty-six non-demented PD patients were assessed by a neurologist on the Ham-D. Patients also completed four mood rating scales: the HADS, the GDS, the VAS and the Face Scale. For the HADS and the GDS, Receiver Operating Characteristics (ROC) curves were obtained and the positive and negative predictive values (PPV, NPV) were calculated for different cut-off scores. Maximum discrimination between depressed and non-depressed PD patients was reached at a cut-off score of 10/11 for both the HADS and the GDS. At the same cut-off score of 10/11 for both the HADS and the GDS, the high sensitivity and NPV make these scales appropriate screening instruments for depression in PD. A high specificity and PPV, which is necessary for a diagnostic test, was reached at a cut-off score of 12/13 for the GDS and at a cut-off score of 11/12 for the HADS. The results indicate the validity of using the HADS and the GDS to screen for depressive symptoms and to diagnose depressive illness in PD.