Movement disorders, such as essential tremor (ET) and Parkinson's disease (PD), are disabling and lower the quality of life of the affected patients. Despite their pathological differences, PD and ET can be difficult to distinguish from each other, due to overlapping symptoms, such as tremor or deficits during motor task performance. Common diagnostic tools, such as polymyography, movement disorder rating scales or single photon emission computed tomography (SPECT) scans are either invasive (SPECT), time consuming, subjective (rating scales), expensive and/or not widely available. Therefore, this thesis focusses on finding objective parameters to differentiate PD from ET that can be measured with commonly available tools.The first objective, quantifying tremor occurrence in ET and PD subjects and identifying corresponding cortical activity, is the topic of chapters 2 and 3. The second objective, quantifying timing deficits of ET and PD subjects during voluntary movement under different conditions and identifying corresponding neuronal networks, is the topic of chapters 4 to 6.In chapters 2 through 5 movement was recorded using accelerometers and muscle activation by surface EMG electrodes. Cortical activity was recorded using EEG in chapters 3 and 5. In chapter 6 brain activation was also measured using functional magnetic resonance imaging (fMRI). Movement was recorded using 3D MRI compatible accelerometers.Chapter 2 describes a new objective quantitative method to split surface electromyography and 3D accelerometer data into tremor and non-tremor windows. Afterwards, the tremor stability index was determined to indicate the advantage of detecting tremor windows prior to analysis. Subjects performed a resting, postural and movement task. Data was split into threesecond windows and the power spectral density was calculated for each window. The relative power around the peak frequency with respect to the power in the tremor band was used to classify the windows as either tremor or non-tremor. The method yielded a specificity of 96%, sensitivity of 85% and accuracy of 91% of tremor classification. During tremor significant differences were found between groups in the tremor stability index. The results suggest that the introduced method could be used to determine