The book covers fundamentals of the radio wave propagation (RWP) theory with application to the forest environments. The emphasis is given to the deterministic and statistical mathematical models as well as to the semi-statistical, semi-deterministic, semi-empirical, and empirical model variants. The book generalizes results of the experimental investigations of the effective complex dielectric permeability of forests, the effective attenuation per unit distance, propagation losses, the effective differential cross-section of scattering and absorption, the effective backscattering area. The wide-spread use of mobile and satellite communication systems as well as applications of the remote sensing of Earth surface and the radio-introscopy of objects inside the forestlands highlight the importance of sophisticated studies which are dedicated to RWP in forests. The solutions of the forest effects on RWP should cover a variety of frequency bands. Therefore, the book, which is to some extent the second part of the book: Popov V.I. Fundamentals of cellular mobile communications of GSM standard, designed for professionals in the field of wireless communications systems (including in the field of cellular mobile communication systems generations G2-G7), and for post-graduate students of universities specializing in the field of radio communications systems.