BACKGROUND: Chemoimmunotherapy (ChIt) has been proven to be an effective treatment for patients with refractory high-risk neuroblastoma (HR-NBL). The objective was to assess the appearance of veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) after high-dose chemotherapy (HDC) and autologous stem cell transplant (ASCT) in patients previously treated with ChIt for refractory HR-NBL. METHODS: Nineteen patients were treated with ChIt based on dinutuximab beta for refractory NBL and underwent ASCT. Six patients underwent HDC with ASCT according to the SIOPEN protocol (Busulfan and Melphalan (BuMel)). Treosulfan and Melphalan (TreoMel) were used in 13 patients. The occurrence of VOD/SOS was analysed. The Mann-Whitney U test was used to analyse the correlation between VOD/SOS and potential risk factors. RESULTS: VOD/SOS developed in five out of six patients when BuMel was used after ChIt (3 pts, grade 4; 2 pts, grade 3), resulting in two deaths. No VOD/SOS was observed in patients receiving TreoMel. Other analysed factors had no influence of VOD/SOS occurrence and the only identified risk factor was BuMel administered after ChIt. CONCLUSIONS: Patients with refractory HR-NBL treated with ChIt and DB did not present life-threatening toxicities or severe liver toxicities during the ChIt cycles and continued to HDC with ASCT according to SIOPEN guidelines. The incidence of severe VOD/SOS after ChIt and subsequent BuMel was higher than expected, with severe course resulting in two deaths. Taking into account the possible increase in the risk of VOD/SOS after BuMel used after chemotherapy combined with DB, careful observation with early VOD/SOS treatment in patients after ChIt is recommended and TreoMel regimen may be considered as less toxic.