The present invention relates to a lithium composite oxide capable of improving capacity and lifetime characteristics of a lithium secondary battery and a lithium secondary battery including the same. According to the present invention, since the atomic ratio of boron (B) and nickel (Ni) in the surface region of the lithium composite oxide including primary particles enabling lithium intercalation and deintercalation and secondary particles formed by aggregating the primary particles is in a specific range, the stability of the lithium composite oxide may be improved, and thus it is possible to improve the capacity and lifetime characteristics of the lithium secondary battery using the lithium composite oxide as a positive electrode active material.