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.