The new hybrid inorganic-organic composites, Ca(10-x)Znx(PO4)(6)(OH)(2)-lactic acid, at different amounts of zinc and lactic acid were prepared by dissolution of the organic compound in an hydroxyapatite suspension. They were characterized by XRD, IR, MAS NMR (C-13 and H-1) and chemical analysis. The crystallinity was slightly affected by the presence of organic fragments. IR and (C-13 and H-1) MAS NMR measurements indicate that the carboxylic groups of the acid interact with calcium and zinc ions of hydroxyapatite surface. Chemical analysis displays that zinc promotes the acid grafting. A mechanism of surface modification is proposed based on the obtained results. (C) 2012 Elsevier B. V. All rights reserved.