Conjugation spaces are spaces with involution such that the fixed point set of the involution has Z/2-cohomology isomorphic to the Z/2-cohomology of the space itself, with the little difference that all degrees are divided by two (e.g. CP^n with the complex conjugation). One also requires that a certain conjugation equation is fulfilled. I give a new characterization of conjugation spaces and apply it to the following realization question: given M, a closed orientable 3-manifold, is there a 6-manifold X (with certain additional properties) containing M as submanifold such that M is the fixed point set of an orientation reversing involution on X? My main result is that for every such 3-manifold M there exists a simply connected conjugation 6-manifold X with fixed point set M
