In this study, detailed analysis of the structural stability of hydrogen bonded four-atom boron clusters within the framework of density functional theory (DFT) is presented. Effects of the number of hydrogen atoms on the structural stability of 134, binding energy of the clusters, and also on the boron-hydrogen binding energy are investigated. Attention is also paid to the determination of energetically the most stable geometries of B4Hn (n = 1-11) boron hydrides, and to their isomers. The lower-lying electronic states of the B4Hn structures are investigated. In addition natural electron configurations of the most stable clusters and charge transfer between the atoms in the cluster are also analyzed. Furthermore, the stability of anionic form of B4H11(-1) cluster is examined. (c) 2006 Elsevier B.V. All rights reserved.