Objectives: The effects and differences of PRP and PRF in bone regeneration have been not indicated clearly. Our experimental studies have shown the favorable effects of platelet-poor plasma (PPP) in bone regeneration. This study evaluated the effect of autogenous plasma and platelet-released growth factors to bone formation. Methods: In vitro study: Blood from healthy subjects was collected, after centrifugation PRP and PPP were taken. The concentrations of platelet-released growth factors in PRP, PPP and whole blood were measured. The proliferation and the differentiation assay were examined using human bone marrow stromal cells. In vivo study: At first, PPP, PRP and PRF were implanted to each extraction socket with dehiscence in canine mandible (n = 12). The extraction sockets of the control group were left unfilled. The morphology in each material of PPP, PRP and PRF was analyzed using SEM. The defects were evaluated at 4 and 8 weeks after surgery and quantification of bone formation was performed. Results: In vitro study: The average concentrations of platelets, TGF-ß1 and PDGF-AB in blood products were all increased in PRP and decreased in PPP. When different concentrations of platelet-released growth factors were added to the human MSC cultures, PRP showed a stimulative effect on proliferation. Contrary to the effect of PRP on proliferation, PRP exhibited an inhibitory effect on osteoblastic differentiation of MSCs in a dose-dependant manner. In vivo study: In SEM analysis, the fibrin network of PRF was most dense. The fibrinogen concentration of PPP was higher than that of PRP. PPP and PRF could sufficiently maintain the bone width and height for the preservation of the socket. However PRP could not maintain the bone width. When bone particles were used as the implant materials, PPP group performed the largest amount of bone. However, bone maturation in the PRF and the PRP groups was more progressed than that in the PPP and control groups. Conclusion: PRP and PRF did not promote bone formation in bone defect site that differentiated osteoblastic cells are few. This study showed that PPP is an effective material for the preservation of sockets with buccal dehiscence and PPP plays a significant role in the presence of fewer osteogenic cells. The fibrin network of PPP has played a role as space making for bone regeneration and would be stimulatory to bone formation. Schlagwörter: bone regeneration, plasma, platelet-released growth factors