Monosymptomatic enuresis in childhood can be divided in two subtypes by a nycthemeral diuresis profile, including urinary volume and osmolality. The first one is characterized by an abnormal circadian diuresis cycle, responsible for nocturnal polyuria and/or low urinary overnight osmolality, there is a good response to desmopressin; the other one is the so-called cognitive or idiopathic type, which provides a poor response to desmopressin.