  We have analysed the X-ray emission from a sample of close WR+O binaries
using data from the public Chandra and XMM-Newton archives. Global spectral
fits show that two-temperature plasma is needed to match the X-ray emission
from these objects as the hot component (kT > 2 keV) is an important ingredient
of the spectral models. In close WR+O binaries, X-rays likely originate in
colliding stellar wind (CSW) shocks driven by the massive winds of the binary
components. CSW shocks in these objects are expected to be radiative due to the
high density of the plasma in the interaction region. Opposite to this, our
analysis shows that the CSW shocks in the sample of close WR+O binaries are
adiabatic. This is possible only if the mass-loss rates of the stellar
components in the binary are at least one order of magnitude smaller than the
values currently accepted. The most likely explanation for the X-ray properties
of close WR+O binaries could be that their winds are two-component flows. The
more massive component (dense clumps) play role for the optical/UV emission
from these objects, while the smooth rarefied component is a key factor for
their X-ray emission.
