Transplantable CD34 hematopoietic stem/progenitor cells (HSPCs) are currently isolated mainly from peripheral blood after mobilization with granulocyte colony-stimulating factor (G-CSF). These mobilized CD34 cells have the potential to generate all blood cell types. For autologous transplantation, the minimal number of mobilized CD34 cells is 2 × 10 CD34 cells/kg body weight. However, up to 30% of patients fail to mobilize enough peripheral CD34 cells after G-CSF treatment. To overcome this limitation, a combination of G-CSF and Plerixafor, a CXCR4 chemokine receptor inhibitor, is proposed to enhance CD34 cell mobilization in poor mobilizer patients. However, only limited data are available on quantification of the functional quality of such patients' mobilized hematopoietic stem cells. Here, for six poor mobilizer patients, a head-to-head comparison of their CD34 cells mobilized without versus with Plerixafor was performed to assess their properties with respect to the reconstitution of human hematopoiesis in vivo in immune-deficient mice. Our results indicate that mobilized CD34 cells recovered after the G-CSF + Plerixafor mobilization protocol have an enhanced intrinsic hematopoietic reconstitution potential compared with CD34 cells mobilized with G-CSF alone.