Room temperature absorption and reflectivity data are presented forCd2P2S6andCd2P2Se6crystals in the range of photon energies between 1.6 and 5.5 eV. For both compounds the characteristic feature of the optical absorption is that their absorption edge appears to correspond to an indirect allowed transition with an optical energy gap of 3.06 eV forCd2P2S6and 2.29 eV forCd2P2Se6.An associated phonon energy of 74 meV forCd2P2S6and 50 meV forCd2P2Se6is also deduced. TheCd2P2X6(withX=Sor Se) reflectivity spectra are compared with the early reflectivity spectrum ofZn2P2S6.As observed in previous reflectivity spectra of theHg2P2X6compounds, near the fundamental absorption edges theCd2P2X6reflectivity spectra show a pronounced rise in reflectivity, a feature common to most layered compounds. For photon energies greater than their absorption edges, the reflectivity spectra of both materials look similar to one another and to that ofZn2P2S6.On the basis of these similarities we have adopted the so-called transition metal weakly interacting model and interpreted the spectral structures as direct allowed interband transitions. For both compounds, these electronic transitions are described by a simplified energy-band scheme. ©1997 American Institute of Physics.