In this paper, the modified Chebyshev planar arrays are introduced. Like Chebyshev planar arrays, they have the important property of providing a constant sidelobe level in all directions. A formula for determining the current distribution in their elements is presented, and an exact formula for directivity is given for even and odd numbers of elements and any direction of maximum radiation. Compared to Chebyshev planar arrays with the same number of elements, same size, and same sidelobe level, the modified Chebyshev planar arrays provide a higher directivity when the number of elements exceeds a minimum value for the specified sidelobe level and interelement spacing. Numerical examples are given to illustrate the features of this new class of planar arrays and to compare their directivity and beam width with those of conventional Chebyshev planar arrays.