Formation of unlimited series of solid solutions of substitution Lasub(1-x)Ysub(x)TiOsub(3) (1) with the structure of rhombic perovskite (sp. gr. Pbnm) is established using X-ray diffraction. With the increase of yttrium content in 1 a distortion of perovskite structure is intensified with the decrease of parameters a and c, increase of parameter b and decrease of unit cell volume V take place. Anomalies on the cirves, expressing the dependences b=f(x) and V=f(rsub(Lnsub(3+))sup(3)) in the limits 1 are connected with considerable distortion of oxygen octahedrons TiO/sub 6/ of LnTiO/sub 3/, where Ln-Sm, Gd and Y.