We report the case of a 27-year-old female who presented with a peculiar story of anosmia fluctuating in a circadian manner. Olfactory function appeared an hour after breakfast, was normal during daytime, and disappeared in the early evening. Imag- ing confirmed chronic rhinosinusitis (CRS). Initial systemic, followed by topical steroid treatment, rapidly and sustainably reversed this condition. The olfactory fluctuation paralleled the endogenous steroid production. This suggests that slight congestion changes in a chronically inflamed nasal mucosa may have been sufficient to induce this circadian anosmia. The importance of identifying fluctuation of olfactory function as a sign of CRS is emphasized and discussed.