Solid solutions of the lithium ion conductor LaLiO2 were synthesized using a solid-state reaction method. For the strontium-doped system, Sr2+ was partially doped at the La sites with the composition La1 - xSrxLi1+xO2 (x = 0.1, 0.2), which introduced excess lithium into the structure, while for the magnesium-doped system, Mg2+ was partially doped at the Li+ site with LaLi1 - 2yMgyO2 (y = 0.1, 0.2) which introduced Li+ vacancies. The magnesium-doped sample with y = 0.1 in LaLi1 - 2yMgyO2 showed higher ionic conductivity of 9.22 x 10(-5) S cm(-1) than that of the respective Sr doped sample of x = 0.1 in La1 - xSrxLi1+ O-x(2) (4.64 x 10(-5) S cm(-1)) at 300 degrees C. Higher ionic conductivity in the Mg doped system indicates that vacancies led to high lithium ion conduction in LaLiO2. The doped LaLiO2 systems are a novel lithium conductive oxides family. (C) 2015 Elsevier B.V. All rights reserved.