The puzzling electronic properties of GaAsN have been investigated through the compositional dependence of two highly sensitive band structure parameters: the electron effective mass, me, and the electron gyromagnetic factor, ge. In the N concentration range from 0% to 0.7%, both me and ge show a highly nonlinear dependence on N composition that can be explained in terms of alternating on‐ and off‐resonance conditions between the red‐shifting conduction band edge and specific energy‐pinned N cluster states. Furthermore, the electronic properties of the material are studied under hydrostatic pressure, P. This allows tuning in a same sample the interaction between extended and localized states and disclosing a hierarchy between different nitrogen complexes as regards the extent of the perturbation these complexes exert on the electronic properties of the GaAs host crystal. (© 2008 WILEY‐VCH Verlag …