Radiation patterns obtained with He-Ne optical masers using plane parallel, confocal and con-centric resonators are described and their dependence on the aperture, on the alignment of mirrcrs and on the exciting power is investigated. It is shown that, with a plane parallel resonator, the spot size of transverse mode depends on the aperture size, but not with a spherical resonator. When the cavity approaches the critical concentric setting, the spot size at the mirror increases and the radiation pattern becomes representative of the lowest order mode. These results obtained are in good agreement with the Boyd-Gordon's theory.