Monophasic samples of La2-xCaxNiO4+delta were prepared in the range between 0 less than or equal to x < 0.4. Their electrical and structural properties were investigated with regard to the excess oxygen delta. Except for the orthorhombic phase with x = 0.1 and delta = -0.01, all members of the system with higher excess of oxygen or calcium are tetragonal with space group I4/mmm. At temperatures below 300 degrees C, the compounds are thermally activated semiconductors; in the range of higher temperatures, the electrical properties are influenced by oxygen exchange, which depends on the calcium doping level.