Epstein-Barr virus (EBV)-associated post-transplant lymphoproliferative disease (PTLD) and adenovirus (AdV)-related pathologies are life-threatening complications of immunosuppression in recipients of hematopoietic stem cell transplantation (HSCT). In certain cohorts (unrelated and haploidentical donor HSCT, T-cell-depleted allograft), the risk of developing these complications is higher. Here we describe the impact of T cell therapy, within programs of specific routine surveillance and preemptive treatment, on the course of EBV infection, and development of related disease, in pediatric recipients of T-cell-depleted, HLA-haploidentical HSCT. Future prospectives include the transfer of this technology to treat AdV-related complications following HSCT.