The present technology relates to a solid-state imaging device that can reduce the power consumption in outputting a low-resolution image, a method of driving the solid-state imaging device, and an electronic apparatus. In the solid-state imaging device, a pixel summing unit outputs a horizontally- and vertically-summed pixel signal by combining pixel signals of pixels that are aligned in a vertical direction and have different weights, and pixel signals of pixels that are aligned in a horizontal direction and have different weights, the pixels being arranged in a matrix fashion. An AD converter unit performs AD conversion on the horizontally- and vertically-summed pixel signal that is output from the pixel summing unit. The present technology can be applied to solid-state imaging devices and the like.