We had the opportunity to employ an anti-scatter grid, which uses fiber as the interspace material. The X-ray transmission rate of fiber is higher than aluminum, so we predicted that the use of a fiber grid would reduce radiation exposure. The purpose of this study was to evaluate the usefulness of the fiber grid. The physical characteristics and influence of focus-grid decentering were compared between the fiber grid and three kinds of antiscatter grids that use aluminum as the interspace material (Al grid). The contrast improvement factor and selectivity of the fiber grid was higher than the Al grid, and the Bucky factor of the fiber grid was lower. The interspace material and grid ratio also influenced focus-grid decentering. The results of this study suggest the potential for reduction of radiation exposure by the use of a fiber grid.