We utilize a semi-empirical sp(3)s* tight binding model to investigate the strain and composition effects on electronic structure of conventional InGaN/GaN and dilute GaAsN/GaAs cubic nitride heterostructures. The model includes the second nearest neighbor (2NN) atomic interactions, spin-orbit splitting and nonlinear composition variation of atomic energies and bond lengths of ternaries. Results show that band gaps of conventional InGaN increase with composition for 0 < x < 1. However, the F band gap of dilute GaAsN decreases with composition for x < 0.25 and then starts to increase for 0.26 < x < 1. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.