Polycrystalline samples of diamagnetically doped Cr 2 O 3 , still being antiferromagnetic, have been investigated by ESR in their high temperature region. In all mixed crystals of [M x Cr 1 - x ] 2 O 3- type with x < 0.15 a variation of the ESR line width according to ΔB(x) = ΔB(0) [1 - αx] was found. While ΔB decreases with x as expected for M = Al, Ga and Sc, it increases for M = In, Y, Lu, La and Bi. This behaviour cannot be explained by magnetic delution alone. By considering the local distortions in an antiferromagnetic compound caused by incorporated foreign ions, a statistical model is developed that describes the observed ΔB(x) behaviour quantitatively.