For any coalgebra C, we can consider the category of all right C-comodules M(c), which is an abelian category. We give a complete characterization of hereditary (pre)torsion theories in M(c). In the first part of the paper we study monomorphism and epimorphism in the category of coalgebras, since they are related to the torsion theories determined by certain morphism of coalgebras with some additional properties (e.g. coflat morphisms).