The electronic band structure and related properties of nanostructured GaAs have been investigated in the frame work of plane-wave pseudopotential approach. The effect of quantum confinement on the electronic, optical and lattice properties of GaAs quantum well has been examined. For bulk GaAs, comparisons between the present results and available experimental and theoretical data previously published in the literature reveal generally good agreement. It is shown that a tremendous variation of the studied properties occurred for quantum well width below 5 nm. The size-dependent electronic properties of nanostructured GaAs is found to be non-linear, whereas the size-dependent lattice and optical properties showed a monotonic behavior. The electronic band structure for both bulk and nanostructured GaAs is analyzed in terms of bonding orbitals. Besides, the electron valence and conduction charge densities derived from pseudopotential band structure calculations are reported and trends in bonding and iconicity are discussed. The information provided from this study may be useful for obtaining derived electronic, optical and lattice properties that were no possible in the unconfined (bulk) GaAs compound semiconductor...