Preservation of function is a crucial aspect for the evaluation of therapies applied in the field of head and neck cancer. However, preservation of Uta Tschiesner 1 anatomic structures cannot automatically be equated with preservation 1 Clinic for Otorhinolaryngology, Ludwig Maximilians of function. Functional outcome becomes increasingly important particularly for the evaluation of alternative treatment options with equivalent oncological outcomes.University (LMU) Munich, Munich, GermanyAs a result, present studies take into account three topic areas with varying emphasis: (1) the effects of cancer therapy on essential physiological functions, (2) additional therapy-induced side-effects and complications, and (3) health-related quality of life. The present article summarizes vital aspects of clinical research from recent years. Functional outcomes after surgical and non-surgical treatment approaches are presented according to tumor localization and staging criteria. Additional methodological aspects relating to data gathering and documentation as well as challenges in implementing the results in clinical practice are also discussed.