Some embodiments include methods of forming photomasks. A stack of at least three different materials is formed over a base. Regions of the stack are removed to leave a mask pattern over the base. The mask pattern includes a pair of spaced-apart adjacent segments of the stack. A liner is formed to cover sidewalls of the segments. Some embodiments include photomasks. The photomasks may include a transparent base supporting a pair of spaced-apart adjacent features. The spaced-apart adjacent features may include sidewalls, with inner sidewalls of the spaced-apart features being adjacent one another, and spaced from one another by a gap. A coating layer of from about 5 Angstroms thick to about 50 Angstroms thick may be along the entirety of the sidewalls of the spaced-apart adjacent features. Some embodiments include methods of photolithographically patterning substrates.