A flaw in the comparison between two different theoretical equations of state for a binary mixture of additive hard disks and Monte Carlo results, as recently reported in C. Barrio and J. R. Solana, Phys. Rev. E 63, 011201 (2001), is pointed out. It is found that both proposals, which require the equation of state of the single component system as input, lead to comparable accuracy but the one advocated by us [A. Santos, S. B. Yuste, and M. López de Haro, Mol. Phys. 96, 1 (1999)] is simpler and complies with the exact limit in which the small disks are point particles.In a recent paper, Barrio and Solana [1] proposed an equation of state (EOS) for a binary mixture of additive hard disks. Such an equation reproduces the (known) exact second and third virial coefficients of the mixture and may be expressed in terms of the EOS of a single component system. They also performed Monte Carlo simulations and found that their recipe was very accurate provided an accurate EOS for the single component system (in their case it was the EOS proposed by Woodcock [2]) was taken as input. The comparison with other EOS for the mixture available in the literature indicated that their proposal does the best job with respect to the Monte Carlo data. Among these other EOS for the binary mixture, only the one introduced by us a few years ago [3] also shares with Barrio and Solana's EOS the fact that it may be expessed in terms of the EOS for a single component system. What we want to point out here is that the comparison made in Ref.[1] is flawed by the fact that it was not performed by taking the same EOS for the single component system in both proposals.Let us consider a binary mixture of additive hard disks of diameters σ 1 and σ 2 . The total number density is ρ, the mole fractions are x 1 and x 2 = 1 − x 1 , and the packing fraction is η = π 4 ρ σ 2 , where σ n ≡ 2 i=1 x i σ n i . Let Z = p/ρk B T denote the compressibility factor, p being the pressure, T the absolute temperature, and k B the Boltzmann constant. Then, Barrio and Solana's EOS for a binary mixture of hard disks, Z BS m (η), may be written in terms of a given EOS for a single component system, Z s (η), aswhere ξ ≡ σ 2 / σ 2 and β is adjusted as to reproduce the exact third virial coefficient for the mixture B 3 , namely β = B 3 (π/4) 2 σ 2 2 (1 + ξ) − b 3 2 .Here, b 3 = 4(4/3 − √ 3/π) is the reduced third virial coefficient for the single component system while B 3 is given by [4]