In this paper, we introduce the concepts of J-prime ideals and MJ-ideals in posets, and obtain some of their interesting characterizations in posets. Furthermore, we discuss the properties of J-ideals that are analogous to J-prime ideals and MJ-ideals in posets. Finally, we establish a set of equivalent conditions for an ideal in a poset P containing an ideal J is an J-ideal, and for a semi-prime ideal J to be an MJ-ideal of P.