In the paper the possibility of the presence of a non-thermal component described by a power law spectrum in the X-ray spectra of OB stars is investigated. The low-resolution spectra of 101 OB stars obtained using the EPIC camera on the XMM satellite are analyzed. It is concluded that the contribution of the non-thermal component of X-ray emission can be significant and even determining for the stars similar to gamma Cas. The inclusion of the non-thermal component in the model X-ray spectra reduces the temperature of the thermal components of the X-ray plasma of such stars down to typical for OB stars values. The contribution of the non-thermal component can also be significant for binary stars with colliding stellar winds and for Of?p stars.