The purpose of the article is to model regular semantic processes taking place during development of the English idioms polysemy. The modeling is carried out with due consideration of cognitive linguistics instruments and is intended to classify polysemy types in the idiomatic domain. The study is novel in that it considers semantic regularity of the English idioms within the frame and conceptual blending theories. It was found that alongside with the radial and chain types of polysemy development there can be distinguished a transition type, the radial-chain polysemy, which is possible due to the nature of interaction between the frames making up the conceptual structure of an idiom.