Nocturia is one of the most bothersome urologic symptoms and may be caused by multiple factors. The urologic diseases leading to nocturia are well understood, however the non-urological causes are often overlooked. Polyuria is usually associated with the medical causes originating outside of the lower urinary tract, whereas decreased bladder capacity is likely a result of urological disease. Identification of the precise type of nocturia and its cause is a prerequisite for the treatment success. This review summarizes the new findings in this area and presents algorithms for differential diagnostics and classification of the symptom.