The paper analyses the morphological and functional features of cord blood cells (CBCs) in the co-culture with multipotent mesenchymal stromal cells (MMSCs) from human adipose tissue under tissue-related oxygen. We have established that MMSCs effectively maintained viability of CBCs at different oxygen concentrations (1, 5 and 20%). According to the data obtained, the oxygen concentration affected the number of colony-forming units (CFUs) formed by CBCs in selective medium. In particular, not co-cultured CBCs the 1 and 5% O2 than at 20% O2. After co-culture with MMSCs, the CFUs numbers were similar at 1 and 20% O2 and increased by 30 at 5% O2. Tissue related O2 concentrations had an impact on the proportion of lineage-resctricted CFCs among CBCs: the number of more committed progenitors--CFU-G and CFU-M, increased, and multi and bipotent--CFU-GEMM and CFU-GM, decreased at low oxygen concentrations. This effect was more pronounced after co-culture compared to that of initial CBCs. Thus, the presence of stromal cells and tissue-related oxygen jointly and severally influenced CBCs in vitro.