Background Rhinosinusitis (RS) is a complex group of disorders characterized by inflammation of the mucosa of the nose and paranasal sinuses. Methods One of the problems with evaluating and treating RS is that there are often difficulties and controversies related to the means of diagnosis, which would prompt appropriate treatment. Results This is particularly true in chronic RS where multiple treatments may be chosen and often these decisions are somewhat empiric and are based on the associated history, symptoms, and prior treatment. This also creates problems with assessing response to treatment where there are multiple tools that are used to diagnose RS and to assess response to both treatment and nontreatment over time. Consistent and reproducible measures of outcome may be lacking. Conclusion The purpose of this study was to describe the various diagnostic criteria that are used to evaluate RS and their role in measuring outcomes.