Little is known about the impact of cytomegalovirus (CMV) infections that occur after human leucocyte antigen (HLA)-matched unrelated donor (MUD) non-myleoablative haematopoietic stem cell transplantation (HCT). We analysed the incidence, onset and outcomes of CMV infections in 59 recipients of MUD and in 109 recipients of HLA-matched related donor (MRD) allogeneic HCT following non-myeloablative conditioning containing 2 Gy total body irradiation and fludarabine. In CMV seropositive recipients, antigenaemia occurred in 68% (MUD) and in 49% (MRD, P = 0.08); there were no differences in the maximum levels of CMV antigenaemia and the time to cessation with antiviral therapy. CMV viraemia by culture was more common in MUD compared with MRD HCT recipients in univariate analysis (26% vs. 6%, P = 0.01), however, this difference was not detectable after controlling for other factors. The rates of CMV disease in the first 100 d were similar in MUD (9%) and MRD (5%) HCT recipients. CMV disease tended to occur earlier in the MUD compared with the MRD recipients (median day 41 vs. day 80). Beyond day 100, rates of CMV disease remained similar in both cohorts (cumulative incidence: MUD 21% and MRD 14%). The 30-d and 1-year survivals after CMV disease diagnosis were not significantly different in both groups. Thus, there appeared to be a trend toward increased CMV reactivation in MUD compared with MRD non-myeloablative allogeneic HCT recipients; however, these differences did not reach statistical significance in this cohort and preemptive therapy was similarly effective in preventing CMV diseases.