Let G be a finite group and W be a subset of G. If ab ≠ ba for any two distinct elements a and b in W, then W is said to be a non-commuting set. Further, if |W| ≥ |X| for any other non-commuting set X in G, then W is said to be a maximal non-commuting set. Fouladi and Orfi determined in [3] the size of maximal non-commuting sets in finite non-abelian metacyclic p-groups. Below we give an elementary proof of this result.