We aimed to evaluate the effects Of L-dopa use on apparent diffusion coefficient (ADC) values of different brain regions in Parkinson's disease (PD) patients. Thirty-five subjects underwent magnetic resonance imaging (MRI), including 21 PD patients (13 men, 8 women; mean age, 63 years +/- 8), and 14 sex and age-matched control subjects. PD patients were separated into two groups according to the duration Of L-dopa usage: patients using L-dopa less and more than I year. According to the disease duration two other groups were formed: patients diagnosed less and more than I year. Unified Parkinson Disease Rating Scale (UPDRS) scores of PD patients were detected. Diffusion weighted images (DWI) and ADC maps of patients and controls were evaluated and regional ADC (rADC) measurements were performed. Patients' age was not significantly different between groups. UPDRS was significantly different between the patient groups. There was no significant difference of rADC values between PD and control groups, and within the different PD groups. Short- and long-term L-dopa usage in PD patients did not cause any change rADC values in various brain regions. (c) 2007 Elsevier Ireland Ltd. All rights reserved.