I'm somewhat of a completist when it comes to European "Exorcist" knock-offs--I've seen at least a dozen of them. This Spanish film is probably closer to the original model than most of the others (but, of course, on a small fraction of the budget of the Hollywood film and nowhere near as effective). The only real thematic differences between this and the American model is that the girl doesn't seem to be possessed by a demon at all, but rather some kind of tall, evil (perhaps hanged?) priest she keeps seeing creepy visions of, and she actually murders people on screen, like her own mother (in a scene that if this movie hadn't been made a year or two earlier, I'd swear was stolen from "The Omen"--maybe "The Omen" ripped-off THIS movie?). The end also takes a pretty different turn.
I saw this mainly for Jack Taylor, but he is pretty much wasted. The main strength though is the possessed girl, played by Inma DeSantis, who actually out-acts her American counterpart Linda Blair and pretty much carries the whole movie herself. The most famous Spanish "Exorcist" knock-off, "Demon Witch Child," has a very creepy pre-pubescent girl as the possess-ee, but the more typical Euro-"Exorcist" m.o. was to cast a "barely legal" teen or adult woman in the role in order to throw in lots and lots of sex (see "The Antichrist", "Malabimba", "The Sexorcist", etc.). This movie kind of tries to have it both ways by casting a pretty but nevertheless slightly underage actress, dressing her in bikinis and skimpy night-gowns, and leering at her a lot, but never actually crossing into anything too overtly sexual. DeSantis would actually have a much racier role only a year later in Eloy Inglesias's notorious "Forbidden Love Games", and she'd go on to an pretty interesting career, but one tragically cut short by a fatal car accident in 1989.
I personally LOVE Euro-"Exorcist" films, even the really bad ones (this one just tends toward mediocre). I'd certainly recommend this to people like myself (hello? . . hello?), but it obviously won't appeal to everyone.