An optical sheet, a backlight unit including the optical sheet and a liquid crystal display including the backlight unit are disclosed. The optical sheet includes a reflective polarizing film, and a first diffusing layer on the reflective polarizing film. The first diffusing layer includes a plurality of first diffusion particles. The first diffusion particles have a volume distribution as a function of diameter. For a diameter D of a first diffusion particle corresponding to a maximum value of the volume distribution, a summation of volumes of a portion of the first diffusion particles having diameters between D−2 μm and D+2 μm is about 40% to 80% of a total volume of the first diffusion particles.