Outcomes of unrelated cord blood transplants (UCBT) were assessed in 172 consecutive children, median age 5 years (range: 0.5-18), with haematological malignancies treated at nine Spanish hospitals between February 1996 and April 2009. Data were collected from the Spanish Working Party for Blood and Marrow Transplantation in Children (GETMON) database. ALL was diagnosed in 125 patients, AML in 43 and myelodysplastic syndrome in 4. Myeloid engraftment (ANC ≥ 0.5 × 109/L) occurred in 87.2% at a median of 22 days and was associated with the total nucleated cell (TNC) dose infused and use of a TT-containing conditioning regimen. Cumulative incidence of relapse was 20% at 1 year post transplant and 29% at 3 years, being higher in patients with a diagnosis of ALL, very high risk disease and GVHD grades 0-1. Cumulative incidence of non-relapse mortality (NRM) was 19% at 100 days post transplant and 39% at 1 year. BU-FLU-TT-ATG-conditioned patients had lower NRM. Disease-free survival (DFS) was 40% at 2 years post transplant (for patients transplanted since 2006). On multivariate analysis, TNC dose infused, AML and BU-FLU-TT-ATG-conditioning regimen increased the probability of DFS. It is of paramount importance to select cord blood units with the highest cell dose. As the BU-FLU-TT-ATG-conditioning regimen was associated with better DFS owing to lower NRM, further prospective studies testing this regimen are warranted.