WRONG Both are put under dresses and skirts to make the fullness that is so adorable and gorgeous. A petticoat gets its fullness from being made of many yards of material, sometimes 60. A crinoline gets its fullness from being made of stiff material such as taffeta or tulle over a silk slip. We prefer Crinolines because they are light and airy while petticoats are a bit smothery and oppressive