A(III)B(V) compounds are important for the development of advanced ceramic semiconductor and nanoelectronic materials, solar cell elements, and light-emitting diodes. A series of these group 13-15 compounds of the general formula M4Y4H8 (M = B, Al, Ga; Y = N, P, As) has been theoretically studied at the B3LYP/TZVP level of theory. The stability of different isomer structures is discussed to reveal the competitiveness of group 13-13, group 13-15, and group 15-15 bonding. Preferential bonding patterns are established, and trends in the stability with respect to M and Y are also discussed. New structural types, featuring perfectly planar M-4 and Y-4 rings, have been established.