The paper presents the methodology for calculation of ferromagnetic resonance spectra of polycrystalline and powder hexaferrites with easy magnetization plane. Magnitudes of magnetocrystalline anisotropy fields and magnetomechanical ratios of the hexaferrites of Ba3Co1.5+хTiхFe24.5–2хO41 (0.0 ≤ х ≤ 1.0) and Ba3Co2.5–хZnxTi0.5Fe23O41 (0.0 ≤ х ≤ 1.2) (0.0 ≤ х ≤ 1.2) systems were determined from an experimental study of the parameters of ferromagnetic resonance at room temperature. The study of temperature dependences of initial magnetic permeability was used to determine the temperatures of spin-orientation phase transitions of these materials. It was shown that substitution of Co2+Ti4+ complex for Fe3+ ions leads to the widening of the temperature region of existence for the magnetic ordering of the easy magnetization plane type with high magnetic permeability in the microwave frequency region. Substitution of Zn2+ ions for some of the Co2+ ions increases the saturation magnetization.