BACKGROUND To increase the number of circulating hematopoietic stem cells (HSC) in the blood, mobilization treatments are currently being used. G-CSF and G-CSF plus chemotherapy are the most common methods of hematopoietic stem cells separation used in Poland. MATERIAL AND METHODS We observed patients who failed an effective hematopoietic stem cell mobilization with G-CSF or with G-CSF plus chemotherapy. The separation was considered unsuccessful if within a period of 4 consecutive days of separation, the number of obtained CD 34+ cells was lower than 2.0×10^6/kg of bodyweight. The study involved 32 patients whose CD34+ cells were collected and the collection for autologous transplantation failed. The study included 20 men and 12 women. Among all 32 patients, 28 had multiple myeloma, 3 had DLBCL lymphoma, and 1 had Hodgkin's disease. RESULTS Separation was unsuccessful in only 3 patients; the remaining 29 achieved an average of 4.83×10^6 CD34+ cells per kg of bodyweight. We conclude that plerixafor is an important tool in obtaining sufficient quantities of cells for hematopoietic stem cells separation. CONCLUSIONS The use of plerixafor is a sufficient and safe option for stem cells mobilization in autologous transplantations.