To the extent that CISG and UNIDROIT Principles address the same issues, the rules laid down in the latter are normally taken either literally or at least in substance from the corresponding provisions of the former. Nevertheless, we may find cases where the latter depart from the former. The purpose of this paper is comparison of the two instruments, especially in part of contract formation. The result of this paper shows the fact that in the chapter of UNIDROIT Principles on formation provisions are included on the manner in which requirements that an offer and an acceptance must meet are more comprehensive, and in result a contract may be concluded more easily.