Abstract: | By using Krasnoselskii's fixed point theorem and upper and lower solutions method, we find some sets of positive values λ determining that there exist positive T-periodic solutions to the higher-dimensional functional difference equations of the form where A(n)=diag[a1(n),a2(n),…,am(n)], h(n)=diag[h1(n),h2(n),…,hm(n)], aj,hj :Z→R+, τ :Z→Z are T -periodic, j=1,2,…,m, T1, λ>0, x :Z→Rm, f :R+m→R+m, where R+m={(x1,…,xm)TRm, xj0, j=1,2,…,m}, R+={xR, x>0}. |