Bothersome symptoms of hay fever impair not only patients' quality of life but also their labor productivity and learning efficiency. Excessive daytime sleepiness (EDS) caused by hay fever is thought to be one of the reasons for these impairments. The purpose of this study was to investigate the relationship between the severity of springtime hay fever and EDS by using a questionnaire. The questionnaire included information about age, sex, height, weight, severity of hay fever, treatment for hay fever, smoking and alcohol consumption habit, history of drug use for sleeping, existence of snoring, and Japanese version of the Epworth Sleepiness Scale. After excluding responses containing insufficient data, responses from 1,734 patients were considered as eligible. By performing logistic regression analysis, we analyzed the effect of the aforementioned parameters on the comorbidity of EDS and snoring. The odds ratio (OR) to comorbid EDS was significantly higher in the moderate and severe hay fever groups than in the asymptomatic hay fever group (moderate: OR=1.76, p=0.014, severe: OR=2.53, p<0.001). Also, OR to comorbid snoring was significantly higher in the severe hay fever group than in the asymptomatic hay fever group (severe: OR=1.90, p=0.001).