New oxoverdazyl ( Vz ·)-substituted dihydrophenazine radical cations ( DPP + ) MCl 4 - (M = Ga, Fe) salts were prepared. The molecular and packing structures, the intramolecular exchange interactions, and the magnetic properties were investigated. The organic part ( VzDPP + ) showed a sizable intramolecular ferromagnetic interaction of J/ k B ⩾ +250 K ( H = - 2 J S Vz · S DPP · + ) between Vz and DPP + , giving S = 1 state at room temperature. Both compounds had very similar molecular and packing structures and there were several intermolecular short contacts between the magnetically important atoms. A 2D type sheet structure was constructed through the contacts between VzDPP + and MCl 4 - moieties in the b– c ∗ plane and a linear ladder chain structure was observed in the a ∗-direction through the contacts between VzDPP + moieties. Thus, the overall intermolecular contacts extend in a 3D manner. The χ p T value gradually decreased by lowering the temperature, indicating antiferromagnetic interactions in both salts. From the temperature dependence of χ p T with consideration of the crystal packing structures, the antiferromagnetic interaction between the VzDPP + spins within the ladder chain was estimated to be in the order of −30 K for VzDPP + · GaCl 4 - . A similar antiferromagnetic interaction between the VzDPP + spins within the ladder chain and a slightly weaker antiferromagnetic interaction between the Fe(III) spins through the ladder chain were observed for VzDPP + · FeCl 4 - .