Sections in In–CaSe and In–CaInSe2 of the ternary system Ca–In–Se have been investigated by methods of physical-chemical analysis and phase diagrams. It has been established that the system In–CaSe is a pseudobinary of eutectic type and the system In–CaInSe2 is nonquasibinary sections of ternary system Ca–In–Se. The confined areas of solid solutions were determined on basis of initial components. It was determined that solid solutions of CaSe are up to 2 mol.% In, and on basis of CaInSe2 they are up to 5 mol.% In