OBJECTIVES: This study examined the association between sleep disorders and lower urinary tract symptoms in patients who had visited urology departments. METHODS: This was an independent cross-sectional, observational study. Outpatients who had visited the urology departments at the Kinki University School of Medicine or the Sakai Hospital, Kinki University School of Medicine, between August 2011 and January 2012 were assessed using the Athens Insomnia Scale and the International Prostate Symptom Score. RESULTS: In total, 1174 patients (mean age, 65.7 ± 13.7 years), with 895 men (67.1 ± 13.2 years old) and 279 women (61.4 ± 14.6 years old), were included in the study. Approximately half of these patients were suspected of having a sleep disorder. With regard to the International Prostate Symptom Score subscores, a significant increase in the risk for suspected sleep disorders was observed among patients with a post-micturition symptom (the feeling of incomplete emptying) subscore of ≥1 (a 2.3-fold increase), a storage symptom (daytime frequency + urgency + nocturia) subscore of ≥5 (a 2.7-fold increase), a voiding symptom (intermittency + slow stream + hesitancy) subscore of ≥2 (a 2.6-fold increase), and a nocturia subscore of ≥2 (a 1.9-fold increase). CONCLUSION: The results demonstrated that the risk factors for sleep disorders could also include voiding, post-micturition, and storage symptoms, in addition to nocturia.