This paper is concerned with S-comultiplication modules which are a generalization of comultiplication modules. In section 2, we introduce the S-small and S-essential submodules of a unitary -module over a commutative ring with such that S is a multiplicatively closed subset of . We prove that if is a faithful S-strong comultiplication -module and , then there exist an ideal and an such that . The converse is true if such that is the set of all units of . Also, we prove that if is a torsion-free S-strong comultiplication module, then if and only if there exist an ideal and an such that . In section 3, we introduce the concept of S-quasi-copure submodule of an -module and investigate some results related to this class of submodules.
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