This paper presents an experimental investigation of diversity gain influenced by polarization and spatial diversity techniques in ultrawideband (UWB) radio technology. To this aim, two different coplanar-fed UWB diversity antennas having the same size and employing identical monopoles were taken and both effective and apparent diversity gain were measured in a reverberation chamber. To extract the diversity gain, three commonly used approaches to combine diversity (i.e., selection, equal gain, and maximal ratio) have been considered. Results showed that >1 dB ( ∼26 %) improvement in diversity gain is obtained over most of the considered band for polarization diversity case as compared with spatial case, showing the usefulness of polarization diversity for future UWB diversity applications. © 2013 IEEE.