A vertical memory device includes a conductive pattern structure on a first region of a substrate, the conductive pattern structure including a stack of interleaved conductive patterns and insulation layers. A pad structure is disposed on a second region of the substrate adjacent the first region of the substrate wherein edges of the conductive patterns are disposed at spaced apart points along a first direction to provide conductive pads arranged as respective steps in a staircase arrangement. A plurality of channel structures extends through the conductive pattern structure and a plurality of dummy channel structures extends through the pad structure. Respective contact plugs are disposed on the conductive pads. Numbers of the dummy channel structures per unit area passing through the conductive pads vary. Widths of the dummy channel structures passing through the conductive pads may also vary.