Tumor occurrence following immunosuppression remains a major concern in children after liver transplantation. More than 50% of these tumors belong to the post-transplant lymphoproliferative diseases (PTLD) and are diagnosed during childhood. These PTLD are mostly related to primary Epstein-Barr virus (EBV) infection and a heavy immunosuppressive regimen. Improvement in their prognosis was reached thanks to a better knowledge of their pathogenesis, risk factors and clinical presentation, linked probably to earlier management. However, their incidence remains stable (occurring in 5-15% of children after liver transplantation) despite different pre-emptive strategies based on these parameters. Moreover, acute graft rejection and subsequent risk of graft loss is a common side-effect of PTLD treatment. EBV viral load determination by quantitative polymerase chain reaction (PCR) is so far the only predictive marker proposed for PTLD prevention and PTLD treatment monitoring, although limited by a lack of specificity. New immunologic techniques have allowed the demonstration of a defect of the EBV-specific cellular immunity in the patients with PTLD. The level of immunity is correlated to the viral load and improves during recovery from PTLD. These recent findings add further knowledge to PTLD pathogenesis and management.