The electronic structure and magnetism are studied for the zinc-blende and wurtzite (Al,Cr)N, (Ga,Cr)N and (In,Cr)N by using the full potential linear muffin-tin orbital method. The energy gap (quasi-gap) in Cr-doped wurtzite InN decreases exponentially with increasing the Cr concentration from 0.027 to 0.166. The half-metallicity is retained in the whole range of concentrations considered, whereas for (Al,Cr)N, the half-metallic character disappears at a concentration of 0.166. The Cr magnetic moment in AlN is about 2.12-2.40µ B Cr atom −1 with changing the Cr concentration, and for Cr in InN, it is a nearly constant value of 3.0 µ B Cr atom −1 .