The electronic structures of nonpolar short-period InN/GaN superlattices grown in the wurtzite a -direction, have been calculated and compared to earlier calculations for polar superlattices (grown in the c-direction). For the nonpolar superlattices it is found that the calculated band gaps and their pressure coefficients are quite similar to those of bulk InGaN alloys with an equivalent In/Ga composition ratio. Also, they are much closer than the values calculated for polar superlattices to the photolu-minescence emission energies and their pressure coefficients measured on polar structures. Possible explanations of the observed phenomena are suggested and discussed. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)