  We have obtained the one--body density matrix and the momentum distribution
$n(p)$ of liquid $^4$He at $T=3D0^o$K from Diffusion Monte Carlo (DMC)
simulations, using trial functions optimized via the Euler Monte Carlo (EMC)
method. We find a condensate fraction smaller than in previous calculations.
Though we do not explicitly include long--range correlations in our
calculations, we get a momentum distribution at long wavelength which is
compatible with the presence of long--range correlations in the exact wave
function. We have also studied $^3$He, using fixed--node DMC, with nodes and
trial functions provided by the EMC. In particular, we analyze the momentum
distribution $n(p)$ with respect to the discontinuity $Z$ as well as the
singular behavior, at the Fermi surface. We also show that an approximate
factorization of the one-body density matrix $\rho(r)\simeq \rho_0(r)\rho_B(r)$
holds, with $\rho_0(r)$ and $\rho_B(r)$ respectively the density matrix of the
ideal Fermi gas and the density matrix of a Bose $^3$He.
