The mechanism of energy transfer in the diphosphate CsY1-xGdxP2O7 (0 < x less than or equal to 1) has been studied both at room and at liquid nitrogen temperatures. Decay curves of the emission arising from the P-6(7/2) state of Gd3+ were analyzed in the entire concentration range. The experimental curves have been fitted with the Yokota and Tanimoto model, assuming a diffusion-limited process. The derived diffusion constant and interaction parameters suggest a temperature dependence of this process.