Using methods of infrared, terahertz, and submillimeter spectroscopy, experimental transmission and reflection spectra of α-lactose monohydrate have been obtained at room temperature in the frequency range from 5 to 5000 cm–1. The experimental spectra of dense pressed tablets and powdered samples have been analyzed in terms of the model of a classical oscillator. Certain parameters of absorption bands of the resonant and quasi-relaxation types are markers by which components can be selected in heterogeneous pharmacological and organic preparations using the methods of coherent submillimeter and pulsed terahertz spectroscopy.