Let G be a group and let w = w(x1, x2, . . . , xn) be a word in the absolutely free group Fn on free variables x1, x2, . . . , xn. The set S (n) (G) of all words w such that the equality w(gσ1, gσ2, . . . , gσn) = w(g1, gn, . . . , gn) holds for all g1, g2, . . . , gn ∈ G and all permutations σ ∈ Sn is a subgroup of Fn, called the subgroup of n-symmetric words for G. In this paper, the groups S (2) (Dp) and S (3) (Dp) for dihedral groups Dp are determined, where p > 3 is a prime. In particular, it turns out that the groups S (3) (Dp) are not abelian.The dihedral group D p is a semidirect product of cyclic groups Z 2 and Z p (for a prime p > 2). It can be presented as the set of all pair (ε, i), where ε = ±1 Algebra Colloq. 2010.17:953-962. Downloaded from www.worldscientific.com by THE UNIVERSITY OF OKLAHOMA on 02/03/15. For personal use only.