Both Beckwith-Wiedemann syndrome (BWS) and hemihypertrophy (HH) have been recognized to be overgrowth syndromes associated with an increased risk of cancer. We report an infant with hepatoblastoma associated with both BWS and HH in whom high serum alpha-fetoprotein (AFP) levels persisted even after complete tumor resection with no tumor recurrence. This phenomenon might be partly due to the nature of the proliferative disease. It is important to recognize that in some infants with BWS prolonged high serum AFP levels mimic the existence of a tumor, and that treatment should be based not only on AFP measurement, but also on repeated radiologic imaging.