The electronic structures of a monolayer quantum well (MLQW) in GaN are investigated by means of the first‐principles full potential linearized augmented plane waves method within the local density approximation (LDA). A super‐cell with periodic boundaries is used to study such systems. It is shown that one InN(AlN) MLQW in the GaN host modifies the localization of charge in the valence band maximum (VBM) and the conduction band minimum (CBM) of In(Al)N/GaN systems. On the other hand the change of the band gap depends on the depth of the MLQW in the GaN matrix. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)