Abstract. We prove that given a finite (zero) exact right decomposition (M, T ) of a semigroup S, if M is defined by a finite complete presentation then S is also defined by a finite complete presentation. Exact right decompositions are natural generalizations to semigroups of coset decompositions in groups. As a consequence we deduce that the Zappa-Szép extension of a monoid defined by a finite complete presentation, by a finite monoid is also defined by such a presentation.It is also shown that when a semigroup A isomorphic to a variant semigroup A(x) that is defined by a finite complete presentation, where x belongs to a sandwich matrix P , together with some other conditions, we deduce that the zero Rees matrix semigroup M 0 [A; I, J; P ] is also defined by a finite complete presentation.