Two-dimensional heterogeneity effects on cell-averaged cross sections and diffusion coefficients have been estimated. Both of the heterogeneity effects caused by the flux fine structure and the resonance shielding are taken into account. The accuracy of several one-dimensional cell models is assessed by comparing cell parameters obtained from one- and two-dimensional cell calculations. The two-dimensional cell heterogeneity effects on core performance parameters have been evaluated for the large fast critical assembly ZPPR-9. The Zebra CADENZA plate-pin experiments have been analyzed using the two-dimensional cell model, and the usefulness of the two-dimensional cell calculation is discussed.