Two children affected by severe aplastic anaemia and sickle cell anaemia rejected the allogeneic bone marrow transplantation from an HLA-matched unrelated volunteer and an HLA-identical sibling, respectively. In both cases a second transplant using granulocyte-colony stimulating factor (G-CSF) mobilized peripheral blood stem cells (PBSC) was performed. Donors were the HLA-haploidentical mother and the same HLA-identical sibling who was employed for the first marrow allograft, respectively. Treatment with G-CSF and PBSC collection were well tolerated. Both patients had engraftment of donor haemopoiesis and did not experience severe graft-versus-host disease. These cases confirm that PBSC transplant should be considered as a feasible treatment to reverse graft failure in paediatric patients.