On-chip photonic devices are often considered in the framework of a two-dimensional (2D) approximation, with light propagating within a defined horizontal plane. Nethertheless, the finite cavity thickness plays an important role in understanding relevant three-dimensional (3D) effects. For instance, the light propagating in the device is diffracted and emitted out of plane if the thickness is comparable to or smaller than the wavelength [1]. Actual 3D microcavities (i.e., cavities where each dimension is comparable in size) were seldom investigated [2]. Here, we evidence that resonances in 3D Fabry-Perot microlasers propagate out of the substrate plane. We also report preliminary results on non-cylindrical microcavity shapes such as cone and pyramid shaped structures which are fabricated by nanoimprinting lithography.