A 62-year-old man presented with a right-sided hemichorea-hemiballismus secondary to underlying non-ketotic hyperglycaemia. This condition is recognised to have a unique finding of unilateral basal ganglia lesion, which is hyperdense on CT and hyperintense on T1-weighted MRI. The clinical course of this condition is benign and has a good prognosis with early correction of the hyperglycaemia.