Background/aim: The data concerning the effects of desmopressin on water/electrolyte disturbances of children with primary monosymptomatic nocturnal enuresis (PMNE) are limited. In the present study we aimed to evaluate the effect and tolerability of desmopressin on blood and urine electrolytes and osmolality in PMNE.Materials and methods: Thirty-five children with PMNE between the ages of 5 and 15 participated in the study. Patients collected urine during the daytime and acknowledged the night time fluid restriction before starting to use the desmopressin tablets. The medication was taken orally at least 1 h before bedtime. Blood and urine samples were collected before the introduction of the treatment (day 0) and on the third and seventh days of the administration of desmopressin to determine osmolality and electrolyte levels.Results: Thirty-five patients participated in the study. Twenty-one patients (60%) were male and 14 (40%) were female. The mean age was 9.6 - 2.7 years. There were no significant changes in serum osmolality, urine osmolality, and serum sodium concentration. Mean urine calcium/creatinine ratio was 0.03 - 0.01 mg/mg at the beginning, 0.06 - 0.02 mg/mg on the third day, and 0.04 - 0.01 mg/mg on the seventh day of the study. No significant changes were seen in urine calcium/creatinine ratio before and after treatment.Conclusion: Desmopressin appeared to be a well-tolerated drug and provided a safe and effective treatment for children who were following fluid intake restriction for PMNE.