Dielectric lenses can substantially improve antenna parameters, especially the planarity of radiated waves and the antenna gain. The paper deals with their application in millimeter-wave band. The main goal concerns the introduction of characteristics and differences between the most commonly used types of dielectric lens antennas, i.e. elliptic and hyperbolic. Their particular features as well as behavior of radiating systems incorporating the lenses are investigated. Specific features of these lenses are discussed for both, near-field and far field based on simulation and measurement results.