The logistic approach in diagnosis of focal nodular hyperplasia (FNH) of the liver is discussed, based on the experience with three children. In only one child could the diagnosis be made without angiography. In that child the combination of hypervascularity on the radionuclide angiogram and uptake of the radiocolloid by Kupffer cells was sufficient for the diagnosis of FNH. If the radionuclide scintigraphy is inconclusive, angiography has to be done to show the typical features of FNH, seen in all three patients. Only if scintigraphy and angiography are not able to differentiate FNH from hepatic adenoma, biopsy or exploratory laparotomy is indicated as a final diagnostic procedure. Ultrasonography or computerized tomography is of value only in screening for hepatic mass lesions.