Background:Oral-functioning impairment can negatively affect the quality of life (QoL) of head and neck cancer (HNC) patients after receiving radiotherapy (RT). Assessment of patient-reported oral functioning throughout treatment can improve patient care. This scoping review aims to propose a definition for oral functioning for HNC patients and to map out the available questionnaires measuring patient-reported oral functioning in RT-treated HNC patients.Methods:A literature search in relevant databases was performed. Each questionnaire was scored on the domains validity, reliability, and responsiveness. Furthermore, the items from the questionnaires were analyzed to define the common denominators for oral functioning in HNC patients.Results:Of the 6434 articles assessed, 16 met the inclusion criteria and employed 16 distinct instruments to evaluate QoL. No questionnaire covered all oral-health-related QoL items nor assessed all aspects of validity, reliability, and responsiveness. Chewing, speaking, and swallowing were the common denominators for oral functioning.Conclusions:Based on the included studies, we suggest using the VHNSS 2.0 questionnaire to assess oral functioning in HNC patients. Furthermore, we suggest to more clearly define oral functioning in HNC patients by focusing on masticatory function (chewing and grinding), mouth opening, swallowing, speaking, and salivation.