The study aims to determine the effects of transplantation of preconditioned human umbilical cord mesenchymal stem cells (hUC-MSC) seeded on a biomimetic 3D scaffold. Methods. Porous collagen 3D scaffolds were prepared by freeze-drying collagen type I solutions. hUC-MSC were isolated by the explant method. The hUC-MSC were preconditioned with H 2 O 2 or LPS for 24 hours, and the cells were seeded onto 3D collagen scaffolds. The effects of MSC preconditioning were studied on the xenogenic transplantation model. The scaffolds isolated five days after implantation were analyzed histologically and by the PCRbased detection of human-specific sequences in genomic DNA extracted from animal tissues. Results. The developed porous collagen scaffolds were able to support the adhesion and growth of hUC-MSC in vitro. The in vivo pro-angiogenic activity was mostly pronounced in hUC-MSC preconditioned with hydrogen peroxide compared to both native and LPS preconditioned hUC-MSC. The data from PCR analysis demonstrated prolonged retention of human DNA in the samples isolated from animals implanted with hUC-MSC preconditioned by low doses of hydrogen peroxide. That might suggest the prolonged survival of the cells in scaffolds upon implantation. Conclusions. hUC-MSC preconditioning with low doses of hydrogen peroxide increases their therapeutic potential.