The Rosenfeld density functional approximation has been considered to investigate the local size segregation and selectivity in the adsorption of a polydisperse hard-disk fluid, which has a continuous distribution of the particle diameter. The calculated results have shown that the preferred species in a circular cavity depend strongly on the size ratio of a polydisperse hard-disk fluid as well as the cavity size and bulk packing fraction. The pore average size distribution for small particles decreases roughly linearly with increasing the cavity size, and the pore average size distribution for an average diameter of particle [sigma] is almost the same as the bulk packing fraction. The local relative concentration oscillates with a spatial period close to the diameter of the large particle as well as the equilibrium density distribution does. These results show that a polydisperse hard-disk fluid confined in a circular cavity rivals similar structural properties compared with those of a multicomponent hard-disk fluid. (C) 2001 American Institute of Physics.