Two cases with hemichorea and dopa induced dyskinesia (DID) were successfully treated with Vim-Vo thalamotomy. The findings of MRI and PET of these cases were variable because of the difference of their underlying disease processes. In the patients with hemichorea, high electrical activities with irregular bursts of discharge were recorded in Vo and Vim. These may be related to dysfunction of Vo underlying choreatic movement. Regardless of the causes, their choreatic movement was abolished by Vim-Vo thalamotomy affecting mainly Vo after physiological identification of Vim.