Radiotherapy (RT) for head and neck cancers causes permanent salivary gland dysfunction (SGD) and xerostomia. We have previously demonstrated the effectiveness of parotid-sparing RT on salivary function. The aim of this was to characterize the relationship between radiation dosages to parotid glands, SGD, xerostomia, and impaired quality of life (QOL). Ninety-three patients received unilateral (n=38) and bilateral (n=44) neck RT with parotid-sparing techniques, or standard three-field technique RT (n=11). Unstimulated and stimulated parotid saliva was collected pre-RT and 1 year post-RT. Assessment of QOL and xerostomia was conducted with three questionnaires. The results demonstrated that reduced radiation dosages to parotid glands were strongly associated with percentage of baseline parotid flow rates measured at 1 year post-RT. Unilateral and bilateral neck RT with parotid-sparing techniques were successful in preserving salivary output, compared to standard three beam RT techniques. Lower radiation dose to contralateral parotid glands was associated with greater percentage of baseline salivary flow rates at 1 year post-RT, fewer xerostomic complaints, and an enhanced QOL.