Inflammatory upper airway diseases, particularly chronic rhinosinusitis (CRS) and allergic rhinitis (AR), have a high worldwide prevalence. CRS and AR involve sustained and exaggerated inflammation that is associated with marked changes in gene and protein expression under tight regulation. A novel group of gene expression regulators is a class of short single-stranded RNA molecules termed microRNAs (miRNAs). miRNAs can cause gene silencing through degradation of target mRNAs or inhibition of translation. Dysregulated expression of miRNAs has been shown in various human diseases, such as cancer, inflammatory skin and bowel diseases, rheumatoid arthritis, and asthma. Although studies of miRNAs in inflammatory upper airway diseases are relatively new and few, emerging evidence implicates an involvement of miRNAs in shaping the inflammation pattern in upper airways. The purpose of this review is to provide an overview on our current understanding of miRNA expression and function in CRS and AR, and to underscore the potential for clinical usage of miRNAs in CRS and AR.