I've been playing SNGs successfully for about a year and hadn't really played many MTTs aside from smaller live ones with less than 60 people.

I too have a really hard time cashing in them. It's a different game than an SNG. For one thing, it's a lot longer, which means you're playing a lot more poker and you're forced to accumulate chips for a longer period of time.

There are more players, which means the minefield is deeper and your journey to the end more treacherous.

With longer play, more players, and a greater chance to step on a mine, variance is obviously going to be a LOT bigger. That is reflected in the payouts, or ROI. You really need to play a lot of them before you have any idea if you're going to be successful or not. In fact, you really need to play a lot of them if you want to get better.

After playing at least two MTTs of 500+ players a day for about a week, I noticed that my performance improved greatly. Practice, studying, and reading here will help your MTT game a lot but don't expect the transition to be a snap or to yield immediate results.

We're probably going through the same kinds of frustration with MTTs but you just have to realize that it's a different form of tournament poker.

Good luck in your MTT pursuits.