A new ordered phase with a composition close to Sr3Ca3Cu6O12±δ has been found in a specimen, prepared by a high-pressure technique, which showed superconductivity. It was found from selected-area diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) studies that this phase has a wavy modulated superstructure, with lattice parameters a\conga c, b≈6a c and c≈6a c, where a c is the cubic perovskite parameter. A tentative structural model based on the two-dimensional ordering of Sr and Ca atoms in the SrCuO2 infinite-layer (IL) basic structure is proposed.