The paper analyzes the contribution of the infrared radiation of the Earth's atmosphere, emitted downward and reflected from the Earth's surface, to the observed spectrum of upward thermal radiation directed to space within the 600-2500 cm-1 range. Surface emissivity for various ecological systems is taken from HITRAN-96 database. As a result of modeling the spectra of the outgoing thermal radiation with the resolution about 0.1 cm-1 with and without the account of the reflected radiation flux we have arrived at a conclusion that the contribution from surface reflectance cannot be neglected if the surface emissivity is below 0.9. In the spectra, the distinctions manifest themselves both quantitatively in wings of relatively strong lines and qualitatively (inversion) for weak lines. Maximum effect is observed at high spectral resolution and if the surface temperature is close to or lower than temperature of the near-ground air. The modeled effects were identified in spectra observed with an IMG sensor installed on ADEOS satellite over the Sahara desert. The necessity is discussed of considering the above effect in the retrieval of atmospheric component profiles from the high-resolution infrared radiation spectra observed from space.