Recently a new three-group clinical classification was reported by an International Consortium to stratify CMML patients with regard to prognosis. The groups were defined as follows: (1) Myelodysplastic (MD)-CMML: WBC ≤ 10 x 10⁹/l, circulating immature myeloid cells (IMC) = 0, no splenomegaly; (2) MD/MP (overlap)-CMML: WBC 10-20 x 10⁹/l or WBC ≤ 10 x 10⁹/l but IMC > 0 and/or splenomegaly; (3) Myeloproliferative (MP)-CMML: WBC > 20 x 10⁹/l. By analysing EBMT Registry patients who underwent allo-HCT for CMML between 1997 and 2016, we aimed to determine the impact of this classification on transplantation outcome and to make a comparison with the conventional WHO classification (CMML-0/CMML-1/CMML-2). Patient grouping was based on the data registered at time of transplantation, with IMC replaced by peripheral blasts. Among 151 patients included in the analysis, 38% were classified as MD-CMML, 42% as MD/MP-CMML and 20% as MP-CMML. With a median survival of 17 months in the whole series, MD-CMML patients were distinguished as a low-risk group with higher CR rate at transplant and a longer post-transplant 2-year progression-free survival in comparison to others (44.5% vs 33.5%, respectively), whereas the WHO classification was superior in identifying high-risk patients (CMML-2) with inferior survival outcomes.