Lot of experimental work has been done on the polytypism of CdI2 and a vast structural data is now available, It is a
theoretical fact that all polytypes consist of basic structures 2H and 4H.In this paper, it has been established that
how the impurities present in the starting material are responsible for “why some of the structures have not been
observed experimentally”. Further, it is suggested that vacancies also play a role in the formation of polytypes.