Аннотация:A comparison is presented of the observed X-ray luminosities from the shock waves formed by the collision of stellar winds in the binary systems WR + O and O + O with close periods and greatly differing mass loss rates, M-dot. Despite the fact that the M-dot values for the star WR in the (WR + O) systems and the brightest O star in the O + O systems differ by 1-2 orders of magnitude, the X-ray luminosities of the shock waves in these WR + O and O + O systems are close to each other within the limits of observational error. This provides evidence that the physical conditions for the formation of the observed X-ray radiation in these two classes of binary systems differ greatly. The causes of this difference - the enhanced absorption of X-ray radiation in the wind of the WR star, the blob structure of the WR wind, the cooling of the hot plasma of the shock wave by inverse Compton scattering, as well as plasma cooling by the radiation in the lines of heavy elements - are analyzed. It is concluded that the hard (E greater than 10 keV) range is particular promising for the investigation of shock waves in the WR + O and O + O binary systems.