Ranging behind hemangiomas, focal nodular hyperplasias (FNH) are the second most common benign solid liver lesions. Women between the age of 20 and 50 years are predominantly affected. In rare cases FNH may occur in children. Etiologically, an arteriovenous vascular malformation of the liver is discussed, which causes pseudotumorous growth of the surrounding liver parenchyma. Morphological features such as the presence of a radial vascular architecture and feeding arteries within a central scar are characteristic for the presence of FNH. Imaging techniques which enable the depiction of the arterial blood supply with a characteristic centrifugal filling pattern, the contrast enhancement in the early arterial phase, the absence of calcifications and of a tumour capsule and the typical enhancement of the central scar, are of particular importance. Knowledge of these features is important in order to differentiate FNH from other hypervascular focal liver lesions with tendency of scar formation, such as hepatic adenomas, giant hemangiomas, hepatocellular and fibrolamellar carcinomas, and metastases. Diagnosis and differential diagnosis of FNH will be enabled by a combined modality approach consisting of (Doppler) sonography and triphasic CT. To confirm the diagnosis of FNH, dynamic MRI is advisable. Because of the invasiveness of angiography as well as the limited sensitivity and spatial resolution of the various scintigraphic methods, these modalities no longer play a role in the diagnostic work-up of FNH. Lesions lacking typical features diagnostic for FNH remain subjects for biopsy and histological examination.