A semiconductor memory device includes stacks on a substrate, each of the stacks including word lines stacked on the substrate and first and second string selection lines laterally spaced apart from each other, vertical pillars passing through the stacks, and first and second bit lines extending longitudinally in a first direction and alternatingly arranged in a second direction crossing the first direction. In a plan view, at least two adjacent ones of the first bit lines in the second direction and at least one of the second bit lines overlap each vertical pillar. A distance between a center of the vertical pillar and one of the first bit lines is different from that between the center of the vertical pillar and another of the first bit lines.