In children, the watery diarrhoea-hypokalemia-achlorhydria (WDHA) syndrome is uncommon and usually due to a neuroblastic tumour hypersecreting the vasoactive intestinal peptide (VIP). We report a case of WDHA syndrome secondary to hypersecretion of VIP that revealed a neuroblastoma in a 13-month-old girl. A secretory diarrhoea, characterised by the persistence of diarrhoea despite the cessation of oral feeding, led to the search of a neuroblastic tumour in the patient. The serum concentration of VIP decreased to normal values soon after the surgical excision of the tumour.