A positive electrode active material, a method of preparing the same, and a positive electrode and lithium secondary battery including the same are disclosed herein. In some embodiments, a positive electrode active material includes a lithium transition metal oxide which contains 60 mol % or more of nickel based on a total number of moles of transition metals excluding lithium in the lithium transition metal oxide, wherein the oxide is in a form of a secondary particle which is an aggregate of primary particles, wherein the lithium transition metal oxide satisfies Equation 1:




1
≤

x
y

≤
20




Wherein x is a minimum area of a rectangle including all pores having an area greater than 0.002 μm2 among closed pores distributed in the secondary particle, and y is a total sum of areas of the pores having an area greater than 0.002 μm2 among the closed pores distributed in the secondary particle.