When I plug my PS3 into my monitor, the quality isn't as good as on my HDTV?

So the problem is that when I'm using my PS3 on my HDTV the quality is superb and I am using an HDMI cable but when I plug the PS3 into my LCD monitor the quality isn't right and I can tell something is wrong. I am also just using the HDMI cable on the monitor. And the problem isn't that my monitor sucks because when I play games via my PC they look great. Any advice is appreciated.