Abstract: Let R be a noetherian ring and S an excellent extension of R. cid(M) denotes the copure injective dimension of M and cfd(M) denotes the copure flat dimension of M. We prove that if M S is a right S-module then cid(M S)=cid(M R) and if S M is a left S-module then cfd(S M)=cfd(R M). Moreover, cid-D(S)=cid-D(R) and cfd-D(S)=cfdD(R).

Key words: excellent extension, copure injective dimension, copure ?at dimension