The present study addresses to systematic consideration of the peculiarities of the surface polaritons (SP) of the phonon and plasmon-phonon types in the porous polar semiconductors InP, GaP and GaAs. The influence of porosity on optical properties was studied theoretically by simulating reflectance and attenuated total reflection (ATR) spectra in the frame of effective medium approximation (EMA) [1]. Three different models of EMA: cavity-Maxwell-Garnett [2], Bruggeman [3] and Monecke [4] were considered and compared. First of them is applicable when crystal part is almost 1, and others are supposed to be applicable for all values of porosity. As seen in fig. 1 for porous system Maxwell-Garnett model can be used when the value of crystal part is in 0.7-1 range. It was shown that with increase of porosity minima in ATR spectra caused by lower and upper mixed plasmon-phonon modes excitation shift toward small wavenumbers. For porous layers with oriented cylindrical or prolate ellipsoidal pores, the optical response should be modeled by an anisotropic layer. Our calculations show than introduction of uniaxial anisotropy (axis is perpendicular to the surface) causes small changes of reflectance and ATR spectra, the value of birefringence is also estimated. Whereas introduction of porous layer with the same free carrier concentration slightly changes the spectra, introduction of depleted porous layer on doped substrate caused a strong effect (fig. 2). Experimental investigations include near-normal reflectance and ATR measurements of the porous layers of polar semiconductor (GaAs, GaP, InP) which were obtained by electrochemical etching [5]. The experimental ATR spectra of porous materials clearly exhibit different changes in comparison of bulk one: shift, splitting or disappearance of the minima corresponding to excitation of mixed surface plasmon-phonon polaritons and also appearance of several additional minima caused probably by vibration modes of oxides. In conclusion, surface polaritons are very sensitive for such parameters of porous semiconductor layers as thickness, porosity, free carrier concentration, etc. Therefore ATR spectra (especially in surface polariton excitation regime) are more informative then reflectance spectra which are usually used. The effective medium approximation may be applicable for porous semiconductor media description in the spectral range of surface plasmon-phonon existence, but the choice of the proper form of such approximation depends on medium topology (matrix, statistical). With the help of the ATR measurements the charge carrier depletion of the porous GaAs layer fabricated by electrochemical etching was experimentally evidenced.