BACKGROUND : Chronic myeloid leukaemia (CML) is very rare in children. The aim of the study is to report the experience within the I-CML-Ped study in children and adolescents presenting at diagnosis with advanced phase disease and to describe their characteristics and outcomes. METHODS : Of 479 children and adolescents enrolled in the international registry for childhood chronic myeloid leukaemia (I-CML-Ped Study; www.clinicaltrials.govNCT01281735), 36 children (7.5%) presented at initial diagnosis with CML in advanced phase according to the European LeukemiaNet criteria. RESULTS : Nineteen (4%) patients were diagnosed in accelerated phase (CML-AP), and among the 17 patients (3.5%) diagnosed in blastic phase (CML-BP), 70% presented with lymphoid immunophenotype. Initial treatment of CML-AP/CML-BP consisted of tyrosine kinase inhibitors (TKIs) with or without chemotherapy, leading to complete haematologic response in 33 of 36 (92%) patients. Seventeen patients proceeded to haematopoietic stem cell transplantation. At the last follow-up, 18 of 19 patients with de novo CML-AP are alive in at least major molecular response (MMR) (n = 16), in progression (n = 1) or in molecular relapse (n = 1) and 13 of 17 patients with de novo CML-BP are alive in at least MMR. Five-year overall survival rates are 94% (95% confidence interval [CI]: 66%-99%) and 74% (95% CI: 44%-89%) for patients diagnosed in CML-AP and CML-BP, respectively. CONCLUSIONS : Children with advanced phase at diagnosis of CML seem to have a better survival rate than that reported for advanced phases evolving under TKI treatment.