Q: Dear Fr. Fortea, where are demons located?
A: Demons—like the souls of deceased human beings—do not occupy space. This does not mean, though, that they are in some other physical dimension. What does being or not being in a dimension mean for a spirit? They are not anywhere. They exist, but they are not “here” or “there” in a physical sense.
A demon is said to be in a place when it acts in that place. If a demon is tempting someone “here,” one says that it is “here.” If a demon possesses a person’s body, we say it is present within the person. If a demon causes a chair to move, we say that he is in that concrete place. In all these cases, though, the demon is simply acting there.
Heaven, hell, and purgatory exist now only as states of being. At the resurrection at the Last Judgment, the souls of the dead will be reunited with their bodies and will then exist in a concrete place (see CCC 650, 1005). At that point, the blessed will occupy a “physical heaven” (that is, a physical place of everlasting happiness), and the condemned will occupy a “physical hell.” As Revelation 21:1 states, “Then I saw a new heaven and a new earth.” After the general judgment, then, the blessed—souls reunited with their resurrected bodies—will dwell in the “new heaven and a new earth” for eternity. Where will condemned humans dwell? We do not know for sure. Some have speculated that the “physical hell” of the damned will exist in the center of this same world.
To learn more about spiritual warfare and demonology, Catholic Spiritual Direction recommends Fr. Fortea’s excellent book, Interview With An Exorcist – An Insider’s Look at the Devil, Demonic Possession, and the Path to Deliverance.