According to Saint Thomas Aquinas any intentional or deliberate sin of lust is a mortal sin.(Summa Theologica, [IIa IIae], The Second Part of the Second Part, Questions 153, 154; SEE: St. Thomas Aquinas's Summa Theologica on the internet at: http://www.ccel.org/a/aquinas/summa/SS/SS153.html
VIEWING PORNOGRAPHY IS A MORTAL SIN. Mortal sin kills the relationship between God and the soul. If a person dies in the state of Mortal Sin they go straight to HELL. This means that a person who views pornography can go to HELL when they die if they don't repent of the sin of viewing PORNOGRAPHY.See the web page on HELL. Supposing a person views pornography, but then repents and turns from their sin. What will happen is that God will save their soul, but He will send them many punishments on this earth and also in PURGATORY. According to the Saints of the Catholic Church who have had visions of PURGATORY, the pains of PURGATORY far exceed any pain we may experience in the body on this earth. See the web page on PURGATORY.
TYPES OF PORNOGRAPHY
Magazines displaying nude or partially nude bodies of women or men for the purpose of sexual gratification.
Movies, including videotapes, CD's, and Lazer-Discs that display nude or partially nude bodies. This would include "R", "X", "XXX" rated movies. Even some PG and PG-13 rated movies are pornographic because of their suggestive content.
Television shows that have nude or partially nude bodies shown with strong suggestive content are forms of pornography that should be avoided. The televisions shows today are filled with this type of material and many people watch these shows not knowing that they are committing grievous sins for which they will be severely punished in hell or purgatory or here on this earth.
Internet sites that display nude or partially nude bodies for the purpose of sexual gratification.
Beaches, where women dress inappropriately in bikini or other immodest clothing. Men who go to the beach and intentionally eye these women are lusting. This is another type of pornography. Women do not have to be completely dressed in the nude to be guilty of dressing in a pornographic nature. The women who dress this way, intentionally exposing themselves, will be punished by God.
Muslim women, while they go to extremes in covering up their bodies, set an example of decency that other women should follow. Muslim women keep their bodies covered in such a manner that keeps men from committing the sin of lust. Their principle of modesty should be followed, but not to such great extremes as completely covering up the entire body. [God's grace work in mysterious way, even in those people who have not yet excepted Christ into their hearts.]
"I see the girls walk by dressed in their summer clothes, I have to turn my head until my darkness goes", from a song by The Rolling Stones, Mick Jagger/ Keith Richards, Paint It Black.
If you look at any of the above you are committing the sin of lust which God will punish here on this earth, in purgatory, and for the unrepentant, in hell. In the Bible, Matthew 5: 27-30, Jesus says:
"You have heard how it was said, You shall not commit adultery. But I say this to you, if a man looks at a woman lustfully, he has already committed adultery with her in his heart. If your right eye should be your downfall, tear it out and throw it away; for it will do you less harm to lose one part of yourself than to have your whole body thrown into hell. And if your right hand should be your downfall, cut it off and throw it away; for it will do you less harm to lose one part of yourself than to have your whole body go to hell."Jesus is telling us that if we look at someone lustfully we commit mortal sin. This would also apply to looking at magazines or videos that have women exposing themselves(pornography). And Jesus gives us a warning saying that it is better to tear out your right eye than to look at someone with lustful intent because the penalty of committing this sin is eternal hell.