The title compounds are structurally isomorphous and crystallize with the symmetry of space group 14/mmm. The lattice parameters are a = 3.8248(1), c = 19.4286(5)Å for La1.9Ca1.1Cu2O6 and a = 3.8601(1), c = 19.9994(5)Å for La1.9Sr1.1Cu2O6+δ. The structure can be easily derived from that of La2CuO4 by substituting the layers of composition CuO2 present in La2CuO4 with a block of three layers having composition and sequence (CuO2) - (R) - (CuO2), where R is Ca, Sr, and/or La. Although the general structural configuration is the same for the Ca and the Sr compounds, the distribution of the metal atoms is different in the two cases. More specifically, in La1.9Ca1.1Cu2O6 the perovskite-type layers form blocks with sequence (CuO2) - (Ca) - (CuO2), and are separated by rock-salt blocks of two layers (LaO) - (LaO). In La1.9Sr1.1Cu2O6+δ, on the other hand, the perovskite-type blocks have composition and sequence (CuO2) - (R) - (CuO2) and they are separated by blocks (NO) - (NO), where both R and N are about 65%La and 35%Sr.