Umbilical cord blood (CB) is increasingly used as an alternative source of stem cells in adult unrelated transplantation. Although registry studies report similar overall outcomes in comparison with BM/PB, comparative studies focusing on severe infections and infection-RM (IRM) with a long follow-up are scarce. A total of 434 consecutive unrelated transplants (1997-2009) were retrospectively analyzed to compare overall outcomes, incidence and risk factors of severe viral and invasive fungal infections in CB (n=65) vs BM/PB recipients (n=369). The 5-year OS was 38 vs 43%, respectively (P=0.2). CB transplantation (CBT) was associated with a higher risk of invasive aspergillosis (100-days-cumulative incidence 16 vs 6%, P=0.04) and CMV infection without differences in RM. No statistically significant differences were found regarding NRM (NRM of 38% in CB vs 37% in BM/PB at 1 year) nor IRM (30% in CB vs 27% in BM/PB at 1 year). In the overall population, NRM and IRM improved in more recent years. In adults who receive a single CBT, the risk of severe infections is increased when compared with unrelated BM/PB recipients, but mortality from infections is similar, leading to similar NRM and survival.