The ternary gallides CeMGa present various structural properties since CeMnGa, CeCoGa and CeCuGa crystallize, respectively, in the cubic MgCu2-, monoclinic CeCoAl-, and orthorhombic CeCu2-type structure. These compounds absorb hydrogen at room temperature but hydrogenation induces a change of the crystalline structure: (i) CeCoGaH3.0 and CeCuGaH0.8 adopt the hexagonal AlB2-type; (ii) on the contrary, the cubic MgCu2 structure is preserved for CeMnGaH1.6. Moreover, in some cases hydrogenation leads to a valence change for Ce. For instance, CeCoGa is considered as intermediate valence compound, whereas CeCoGaH3.0 contains Ce3+. This paper demonstrates that hydrogenation strongly influences the Kondo effect in these intermetallics.