The paper presents volume modification of polyacrylonitrile (PAN) fibers with silver nanoparticles and their influence on the structural, thermal and mechanical properties of obtained fibers. A polymer-silver composites were obtained by a new method based on preparation of nanoparticles directly in fibers forming solution. The spinning solution contained PAN and AgNO3 was dissolved in the DMF. The PAN(Ag) fibers were characterized by various methods. The results showed that doping PAN fibers with silver nanoparticles has a significant influence on every measured parameters and clearly indicated the relationship between them. The XRD studies have shown that the degree of crystallinity was bigger in PANAg than in pure fibers. By the FTIR, DSC and TG methods it was indicated that in PANAg dehydrogenation than cyclization process is preferred. The analysis of the mechanical properties of the fibers showed that PANAg are characterized by greater strength and Young modulus, as well as a lower elongation than PAN. (C) 2015 Elsevier Ltd. All rights reserved.