J.M. Kim 1 , S.K. Hwang 1 , B.H. Choe 1 1 Department of Pediatrics, Kyungpook National University Hospital, Daegu, Korea Backgrounds: By analyzing the characteristics of children with chronic hepatitis B who have lost HBsAg by long-term lamivudine treatment, the selection of target patients could be relevantly predictable in the treatment of chronic hepatitis B in children. Methods: A total of 75 HBeAg positive children (< 18 y-o) were recruited who have visited Kyungpook National University Hospital from Mar. 30, 1999 to May 8, 2008 . They were treated with lamivudine for at least 6 months. HBeAg seroconversion occurred during lamivudine treatment in 49 out of 75 children. They were divided into HBsAg clearance and non-clearance group. Parameters influencing treatment results were analyzed according to HBsAg loss. Result: Thirteen out of the 49 (26.5%) patients with HBeAg seroconversion were classified as HBsAg clearance group, while 36 (73.5%) as non-clearance group after lamivudine treatment. Twenty five of 49 patients with HBeAg seroconversion were under 6 years old, in 10 (10/25, 40%) of whom HBsAg loss occurred as well. Twenty four of 49 patients were over 6 years old, in 3 (3/24, 12.5%) HBsAg loss occurred, that showed significantly difference (p-value= 0.029, OR: 4.667, CI: 1.094-19.902) compared to younger group. Age was significantly lower in HBsAg clearance group (5.1±4.3 years) than non-clearance group (8.2±5.0 years) (p=0.043), but no difference was observed in other parameters. Anti-HBs appeared in 12 patients. Conclusion: In the treatment of HBeAg positive chronic hepatitis B with lamivudine, age was significantly lower in HBsAg clearance group than non-clearance group. Background: Dysfunction of T cells may represent a mechanism of hepatitis B virus (HBV) persistence. Programmed death-1 (PD-1) and its ligands, PD-L1/PD-L2, are members of CD28/B7 family, was reported to transfer inhibitory signal, leading to the dysfunction of T cell.