In the present study, we addressed the question of how often HLA-DRB1-matched donors can be found by further typing of AB-matched donors and whether Cw preselection can be helpful. Sixty-eight patients and 174 donors were enrolled in the study. In all donors, confirmatory DNA Cw typing was performed to check reliability of registry Cw data. Among the 129 Cw serologically typed donors, 11 (8.5%) were not confirmed by DNA typing and for 77 (60%) at least one Cw blank antigen was genetically confirmed. In healthy controls, haplotype frequency higher than 1% has been found for 21 (55%) out of 38 Cw-DRB1 haplotypes observed. A subtotal delta made up 67% of subtotal haplotype frequency fraction of 21 haplotypes confirming strong linkage disequilibrium of Cw-DRB1 loci. After Cw preselection 12 (15.4%) out of 78 donors were matched in both DRB1. On the other hand, only two (2.1%) out of 96 AB-matched donors with unknown or incompatible Cw were matched in both DRB1 at low-resolution level (OR = 8.55; P = 0.0060; 95%CI 1.85-39.5). We found at least one DRB1-matched donor for 12 (26.1%) out of 46 patients with Cw-matched donors for which 1-5 (median = 1) of Cw-preselected donors were chosen for further typing. Cw preselection of HLA AB-matched donors for further DRB1 typing may improve the efficacy of stem cell donor search process.