Central diabetes insipidus, is a syndrome characterized by the excretion of abnormally elevated volumes of diluted urine, due to the diminution of reabsorption of water in the collecting ducts, induced by the diminution of production of antidiuretic hormone. The involvement of the central nervous system in the leukaemia is frequent, but the association leukaemia/diabetes insipidus is rare. We describe a clinical case of a 40 years old female, whose first manifestation of leukaemia was diabetes insipidus; we discuss the difficulties of diagnosis, the particularities of the case and its evolution.