Samples of CdIn2Se4 were produced by the melt-and-anneal technique, annealing at 500 degrees C giving samples of the beta -structure. Measurements of optical absorption were carried out in the temperature range 20-300 K and the data analysed to give values of the indirect and direct gap, E0I and E0D, respectively, at each temperature. The variations in E0I and E0D with temperature were fitted to a simplified Manoogian Leclerc equation and the fitted coefficients used to give values of (dE0/dT)1, due to electron-phonon interaction, and (dE0/dT)2, due to lattice dilation, for each gap. Hence the values were determined for the deformation potentials of the valence and conduction bands.