New calix[4]arene phosphoryl derivatives have been synthesized, starting from a calix[4]arene (cone conformer) bearing four P(O)-H functional groups at the wide rim as synthon. Their binding properties towards trivalent lanthanide and actinide cations are investigated by complexation studies in methanol, and liquid-liquid extraction studies. The carbamoylmethylphosphine oxide and diphosphine dioxide derivatives display the 'calixarene effect', i.e., they are more efficient than their constitutive binding sites. The studies also reveal the importance of the attachment mode of CMPO-functions to the calixarene platform for the cation binding properties.