A skew morphism of a finite group $A$ is a permutation $\varphi$ of $A$ fixing the identity element and for which there is an integer-valued function $π$ on $A$ such that $\varphi(ab)=\varphi(a)\varphi^{π(a)}(b)$ for all $a, b \in A$. A skew morphism $\varphi$ of $A$ is smooth if the associated power function $π$ is constant on the orbits of $\varphi$, that is, $π(\varphi(a))\equivπ(a)\pmod{|\varphi|}$ for all $a\in A$. In this paper we show that every skew morphism of a cyclic group of order $n$ is smooth if and only if $n=2^en_1$, where $0 \le e \le 4$ and $n_1$ is an odd square-free number. A partial solution to a similar problem on non-cyclic abelian groups is also given.