The present invention provides a lithium-transition metal composite oxide having a large volume capacity density, high safety, excellent coating uniformity, excellent charge/discharge cycle durability and excellent low temperature characteristics, and suitable as a positive electrode active material for a lithium secondary cell. A lithium-transition metal composite oxide which is represented by the formula Li_xM_1-;yN_yO₂ (wherein 0.2x1.2, 0y0.7, M is a transition metal element, and N is a transition metal element other than M or an alkaline earth metal element), wherein in the distribution curve of the cumulative volume particle size of said lithium composite oxide, the inclination of the curve at a cumulative volume fraction of 20% and 80% are at most 9%/m and at least 3%/m, respectively, and the average particle size is from 3 to 20 m.