Background: It is known that the synthesis of nitric oxide (NO) is increased in cirrhosis. In humans, NO levels were investigated mostly in adult cirrhotics with portal hypertension. Because there is no study investigating NO status in childhood cirrhosis and because Wilson's disease (WD) has some specific properties due its copper overload with powerful prooxidant action, we aimed to determine serum NO levels in children with untreated WD and to investigate the probable relationship between NO level and both clinical presentation and the severity of the disease. Methods: Twenty children with newly diagnosed WD and sex and age matched 14 healthy children were included. Serum NO levels were determined by spectrophotometric method using Griess reaction. Results: Serum NO level of children with WD and of healthy children were 156.8 +/- 28.2 and 135.6 +/- 21.17 mu mol/l respectively (p = 0.024). Serum NO level was not different in respect with the clinical presentation, such as presence of ascites, neurological involvement, cholestasis or haemorrhagic diathesis. Severity of the disease did not influence the serum NO level. Serum NO levels of patients with low and normal ceruloplasmin levels were not different. Conclusions: It was demonstrated that serum NO level was higher in children with WD compared to healthy children. Because we could not find a correlation between raised NO and any clinical or biochemical findings in the present study, we concluded that NO could not be used as a prognostic or predicting factor in children with WD.