The potential energy curve of hydrogen fluoride was calculated using the Ornstein-Uhlenbeck diffusion quantum Monte Carlo method. There are two choices in the determination of the trial wave function: a full optimization of all parameters of the trial wave functions and a partial optimization of the coefficients of different configuration wave functions. A full optimization gave an excellent result while comparing with results of other theoretical calculations as well as the experiment. A partial optimization described a wrong behavior in large separation but provided a good alternative in calculating the behavior near the equilibrium distance while considering the computational demandings. (C) 2003 Elsevier B.V. All rights reserved.