A number of potentially poisonous mushrooms are superficially similar but do not match all the key characteristics. The less common Coprinopsis romagnesiana
differs in that the cap is covered with darker brown appressed scales and lacks granules when young. It interacts with alcohol in a similar way to Coprinopsis atramentaria
. The edible Coprinellus disseminatus
differs is smaller (under 2 cm broad), lacks granules on the cap, and does not become inky when old.