Abstract In the spinel compounds of ACr2 X 4 type, and in the spinel series of Zn1−xGa2x/3Cr2Se4, ZnCr2-xInxSe4, Zn1−xCuxCr2Se4 and Li1+xTi2-x,O4, the influence of vacancies and mixed valence on the transport processes is considered. For this purpose, a procedure of calculation of the ion packing coefficients was used and calculations of the fulfilment coefficient, the difference of the Pauling electronegativities and the vacancy parameter were introduced. For the spinel compounds of ACr2 X 4 type (where A=Zn, Cd, Mn; X=O, S, Se) the vacancy parameter strongly increases with an increase of the anion radius. The vacancy parameter was found to decrease most with an increase of the imperfection degree of the spinel structure in Zn1−xGa2x/3Cr2Se4. For the spinel series ZnCr2-x, InXSe4, the vacancy parameter remains almost constant with an increase of the In concentration. For the spinel series Zn1−xCuxCr2Se4, the appearance of the Cr mixed valence with an increase of x makes the carrier transport easier, lead...