Purpose: The aim of this study was to determine the causes and impacts of diagnostic delay in head and neck cancer.Material and methods: A search was conducted to identify studies that described the association between diagnostic delay in head and neck cancer and prognosis. Studies were assessed with checklists for evaluation of scientific literature, published by The Norwegian Knowledge Centre for Health Services, and graded according to The Health Technology Assessment. A total of 30 relevant studies were analyzed. Causes of early and delayed diagnosis and impacts of delayed diagnosis were extracted and the results were sorted accordingly.Results: Inadequate medical examination, comorbidity, being a non-smoker, female gender, omitting yearly dentist’s appointment, being overlooked at initial doctor’s visit and being of a low socio-economic status are associated with delayed diagnosis. Some studies have also shown that diagnostic delay reduces survival. Delayed radiation therapy is also associated with poor local control of the cancer.Conclusion: Diagnostic delay is associated with reduced survival. In particular, general practitioners should be aware of the condition’s initial symptoms and they should make sure not to overlook them. Too many patients have been treated with antibiotics by doctors who have misinterpreted cancer symptoms.