Cement mortar was reinforced with coal tar pitch-derived C fibers (0.5% by mass) and silica fume treated with concd. HNO(3) before their use to produce OH and COOH groups on their surface and improve their wettability. The reinforcement resulted in an increase in the bending and compression strength of the cement composites. The chem. modification of the fiber surface did not contribute, however, to any improvement of the mechanical properties of the composites, except for their flexural toughness defined as a surface under the bending stress vs. displacement curve.