Introduction. The blood supply and growth factors are essential factors in postoperative healing. Platelet-Rich Fibrin (PRF) is a relatively new concept of natural tissue regeneration, which is widely applied in oral and maxillofacial surgery. Its’ advantage consists in increased concentration of autogenous growth factors. It may be used alone or in combination with grafting materials, in order to facilitate wound healing, bone growth and tissue maturation after different types of surgeries.   Aim of the study. The aim of this study is to analyze the effect of Platelet- Rich Fibrin (PRF) regarding specific clinical cases, in patients with different diagnosis.   Material and methods. A clinical study has been performed in four patients with different clinical diagnosis: wound dehiscence, oro-antral communication, mandibular cyst, free gingival graft from palate. These patients were treated using standard treatment protocols and the Platelet- Rich Fibrin membranes as biological seals with and without grafting materials.   Results. The use of PRF membranes as biological seal after soft tissue grafting as well as tooth extraction with cystectomy appeared to be stable and protected the socket and grafting material during healing. The same effect was observed after closing of oro-antral communication. Furthermore, the application of PRF membranes seems to promote tissue healing in case of postoperative wound dehiscence.  Conclusions. The use of PRF membranes has a positive effect upon soft and hard tissue healing. Moreover, it seems to facilitate the healing process and decrease the risk of postoperative complications.