Abstract Purpose Nocturia is one of the most bothersome lower urinary tract symptoms (LUTS). The aim of the prese study is to determine whether severe-nocturia have impact on the abnormal daytime sleepiness in men wit LUTS/benign prostate hyperplasia (BPH). Materials and Methods Severe-nocturia was classified as twice or more per night. A total of 85 men met th criteria and constituted the study cohort. The patients had a detailed clinical evaluation, including a complete histor physical examination, urine analysis, urine culture, a digital rectal examination, serum prostate-specific antigen (PSA level, prostate volume by transrectal ultrasonography, uroflowmetry and postvoid residual urine volume. LUTS an symptom-specific quality of life (QoL) were assessed using the IPSS. Patients were asked to complete an Epwort Sleepiness Scale questionnaire for daytime sleepiness. Results 43 patients had less than one, 42 patients had more than two episodes of nocturia. There was no significa difference of age, total prostate volume, PSA levels between patients with mild-nocturia and severe-nocturia. Ther was no significant difference of maximum flow rate (Qmax), voided volume and postvoid residual urine volume (PV between patients with mild-nocturia and severe-nocturia. There was significant decrease of total International Prostat Symptom Score (IPSS) scores and QoL index in patients with severe-nocturia compared in patients with mild-nocturi The number of patients with abnormal daytime sleepiness in mild-nocturia and severe-nocturia were 4.7% (2/43 16.7% (7/42), respectively (p<0.05). Regression coefficiency between percent of nocturia and total score of daytim sleepiness was significant (p<0.05) and regression coefficient (R) was 0.29. Conclusions Our results indicate that severe-nocturia had impact on the abnormal daytime sleepiness in patient with LUTS.