To verify the performance of the fixed-node diffusion quantum Monte Carlo method in electron affinities calculations, the adiabatic electron affinities of C-2 and BO molecules calculated by the fixed-node Ornstein-Uhlenbeck diffusion quantum Monte Carlo simulations guiding by trial wave functions constructed from the floating spherical Gaussian orbitals and spherical Gaussian geminals are presented in this work. The random walk based results, 3.264(43) and 2.507(32) eV for C-2 and BO, respectively, are compared with the available best experimental determined values, 3.269(6) and 2.508(8) eV for C-2 and BO, respectively, and the results of other theoretical calculations. (C) 2004 American Institute of Physics.