Microdialysis of the basal ganglia was used in parallel to deep brain stimulation (DBS) for patients with Parkinson's disease. The aim of this study was to patient-specifically simulate and visualize the maximum tissue volume of influence (TVI(max)) for each microdialysis catheter and the electric field generated around each DBS electrode. The finite element method (FEM) was used for the simulations. The method allowed mapping of the anatomical origin of the microdialysis data and the electric stimulation for each patient. It was seen that the sampling and stimulation targets differed among the patients, and the results will therefore be used in the future interpretation of the biochemical data.