Head and neck cancer (HNC) shares some risk factors with cardiovascular disease. Neck radiotherapy (RT) causes carotid artery injury and stenosis. In HNC patients treated with RT, the prevalence rate of severe (>70%) carotid artery stenosis is >10%, and the cumulative incidence continuously increases over time. There is at least a two-fold risk of cerebrovascular events in these patients compared with the normal population. Carotid artery stenosis is mainly assessed and diagnosed via duplex ultrasonography. Angioplasty and stenting may be recommended to patients who developed severe post-irradiation carotid artery stenosis. This review assessed Taiwanese data that provided some recommendations for HNC patients treated with RT. With consideration of the high prevalence rate of carotid artery stenosis after neck irradiation, duplex ultrasonography should be included in the follow-up workup.