This study investigated the neural correlates of hypophonia in individuals with Idiopathic Parkinson’s disease (IPD) before and after the Lee Silverman Voice Treatment (LSVT), using 15O-H2O Positron Emission Tomography (PET). Regional cerebral blood flow (rCBF) changes associated with overt speech-motor tasks relative to the resting state were measured in the IPD subjects before and after therapy, and in a group of healthy controls. Before LSVT, patients had strong speech- related activations in motor and premotor cortex, supplementary motor cortex and inferior lateral premotor cortex which were significantly reduced post-LSVT. In addition, significant right-sided activations were present in anterior insular cortex, caudate head, putamen, and dorsolateral prefrontal cortex following LSVT. Finally, the LSVT-induced neural changes were not present with transient experimenter-cued increases of loudness in LSVT-untreated patients. This treatment-dependant functional reorganization suggests a shift from an abnormally effortful to a more automatic implementation of speech-motor actions.