[en] A comparative spectroscopic study for Ho³⁺ and Ho³⁺, Yb³⁺ doped CdF₂ crystals has been realised at liquid nitrogen temperature. The Ho³⁺ single-doped sample shows principally blue emission corresponding to the ⁵F₃→⁵I_g transition, whereas the Ho³⁺, Yb³⁺ codoped sample gives rise to a very efficient green emission which is ascribed to the ⁵F₄, ⁵S₂→⁵I_g transition. The total integrated upconversion emission intensity (including blue and green emissions) for the codoped crystal is three times more intense than that of the Ho³⁺ doped one, while the ratio for green emission rises to 27. The green emission in the codoped sample results mainly from the Ho³⁺-Yb³⁺ mixed centre, whereas the blue emission is essentially due to the Ho³⁺-Ho³⁺ pair. Two energy transfer upconversion mechanisms have been proposed and are discussed in the paper. (author)