Compounds in a CaO-Y2O3-SnO2 system were prepared by a solid-state reaction at 1673 K. The phase relation in this system was investigated by powder X-ray diffraction. Besides the previously reported ternary compounds, CaSnO3, Ca2SnO4, Y2Sn2O7, and a quaternary compound Ca0.4Y1.2Sn0.4O3, solid-solution series of Ca2-xY2xSn1-xO4 with 0 <= x <= 0.5, and Ca1-yY2ySn1-yO3 with 0 <= y <= 0.2 and 0.95 <= y <= 1.0 were found. The cell parameters of these solid-solution series were refined. The changes of rhombohedral cell parameters in the samples prepared in the range 0.565 < y < 0.714 of Ca1-y Y2ySn1-yO3 suggested the existence of solid solutions of Ca0.4Y1.2Sn0.4O3, although their single phases could not be prepared, except at y=0.6.