Functionalization of isotactic polypropylene (i-PP) with citraconic anhydride (CA) was carried out in 1,2,4-trichlorobenzene solution with dicumyl peroxide as an initiator at 160 degrees C under nitrogen atmosphere.atmosphere. Chemical and physical structures and thermal behavior of the synthesized graft copolymers with different anhydride units were determined by volumetric titration (acid number), FTIR and H-1-NMR spectroscopy, X-ray powder diffraction, DSC and TGA thermal analyses. It was shown that the crystallinity and thermal behavior of grafted i-PP's depend on anhydride unit concentration in grafted i-PP; grafting reaction proceeds selectively which is not accompanied by oligomerization of CA and degradation main chain as in known maleic anhydride/PP system. This fact was explained by inhibition effect of alpha-methyl group in CA grafted unit on the chain beta-scission reactions and no homopolymerization of CA in chosen grafting conditions. Functionalized i-PPs showed high thermal stability in comparison with virgin i-PP.