To investigate which reduced-intensity conditioning (RIC)/reduced-toxicity conditioning (RTC) is superior for umbilical cord blood transplantation (UCBT) for lymphoid malignancies, we retrospectively compared three widely used RIC/RTC regimens: fludarabine/melphalan/total body irradiation (FM-TBI, n = 524), fludarabine/cyclophosphamide/total body irradiation (FC-TBI, n = 96), and fludarabine/busulfan/total body irradiation or melphalan (FB-based, n = 159). Among patients with acute lymphoblastic leukemia (ALL) (n = 314), there were no differences in overall survival (OS) by conditioning regimen. Among patients with malignant lymphoma (ML) (n = 465), FM-TBI and FC-TBI regimens had similar OS, whereas FB-based regimen had lower OS (hazard ratio [HR], 1.73; P