Hypersplenism is frequently associated with liver cirrhosis and commonly presents itself as splenomegaly with hematological disorders. The purpose of this study was to clarify the effect of orthotopic liver transplantation (OLT) on splenomegaly in pediatric group of patients with functional grafts. In 5-year-period, from July 1999 to June 2004, 33 pediatric patients (1-17 years old) underwent OLT. 7 patients who died in the first month after the surgery were excluded from the study. Among 26 patients, 1 with transplanted hepatic artery occlusion and 4 with acute rejection had non-functional grafts. 21 patients’, with functional grafts, preoperative and postoperative one week, one month, three months, six months, and twelve months follow up spleen size measurements were obtained. Spleen sizes had been measured by using ultrasound (US). The data was evaluated using Wilcoxon Signed Ranks Test to see whether the decrease in spleen sizes was significant in patients with functional grafts. In 21 pediatric group of patients, spleen sizes decreased after the surgery and this was statistically significant in one week, one month, three months, six months, and twelve month follow up measurements (P< 0.05 for all follow up measurements). The normalization of spleen size can be expected in pediatric group of patients with functional liver grafts, and US is a simple and cheap radiological technique for follow up measurements.