Abstract. We show that if X, Y are smooth, compact k-dimensional submanifolds of R n and 2k + 2 ≤ n, then each diffeomorphism φ : X → Y can be extended to a diffeomorphism Φ : R n → R n which is tame (to be defined in this paper). Moreover, if X, Y are real analytic manifolds and the mapping φ is analytic, then we can choose Φ to be also analytic.We extend this result to some interesting categories of closed (not necessarily compact) subsets of R n , namely, to the category of Nash submanifolds (with Nash, real-analytic and smooth morphisms) and to the category of closed semi-algebraic subsets of R n (with morphisms being semi-algebraic continuous mappings). In each case we assume that X, Y are k-dimensional and φ is an isomorphism, and under the same dimension restriction 2k + 2 ≤ n we assert that there exists an extension Φ : R n → R n which is an isomorphism and it is tame.The same is true in the category of smooth algebraic subvarieties of C n , with morphisms being holomorphic mappings and with morphisms being polynomial mappings.