Using first-principles density functional calculations, the effect of high pressures, up to 30 GPa, on the structural, elastic and electronic properties of SiX₂O₄, with X = Mg, Zn and Cd, was studied by means of the pseudo-potential plane-waves method. We used both the local density approximation and the generalized gradient approximation to the exchange-correlation approximation energy. The results of bulk properties, including lattice constants, internal parameters, bulk modulus and derivatives, are obtained. The elastic constants and their pressure dependence are calculated using the static finite strain technique. We derived the bulk modulus, shear modulus, Young's modulus and Poisson's ratio for ideal polycrystalline SiX₂O₃ aggregates. We estimated the Debye temperature of SiX₂O₄ from the average sound velocity. Band structure, density of states and pressure coefficients of some gaps are also given. This is the first quantitative theoretical prediction of the elastic and electronic properties of SiMg₂O₄, SiZn₂O₄ and SiCd₂O₄ compounds, and still awaits experimental confirmation.