Using a model system of 4,4'-biphenyl-substituted alkaneselenols on (111) gold and silver substrates, we show that the hybridization and, thus, spatial orientation of the binding orbitals of selenium is a determining factor for the molecular packing and structure of alkaneselenolate self-assembled monolayers (SAMs). Considering that a similar effect has been previously observed for the sulfur headgroup in alkanethiolate SAMs, its generality for different SAM systems can be assumed.