Absolutely agree! Lying is a big NO-NO for most people. So you need to re-assess the situation. Most people don't change and if they do it's because they have decided to, not because they're trying to change for someone or something - in other words, if it's gonna stick, he's got to decide to do it for himself.
So if he won't? you need to ask yourself if these are NO-NO's you can live with...
Can you learn to live with a man who has a p 0 r n addiction?
Can you learn to live with a man who lies?
The lying possibly stems from the p 0 r n (because it is an addiction) and the guilt he probably feels when he looks at it all ties into the nastiness of addiction - so is the lying and the hiding and sneaking around. It's all in the nature of addiction.
Maybe you could talk to him in the terms of getting help with the problem but most guys don't see this as a problem (they're taught from such a young age that men should ALWAYS want to ogle naked women and it's perfectly normal).
I've dated several guys who were p 0 r n freaks, I'm actually dating one now, it isn't one of those things that really bothers me and so he has no reason to lie about it but the funny thing is that he still tries to hide it... even though he KNOWS I won't get mad, or even care! It's so ingrained that it's dirty to look at p 0 r n - and then the double standard that they should WANT to anyway! Man, it's a wonder that all the guys out there aren't sexual deviants!