Creating modules to maintain structure

I’d like to have your opinion in creating modules for a quite large scale web application, my thought is that by doing that for example when building a web shop, administration and statistics etc that this will create a better structure for the application, which experience do you have?

I’m new to Yii, but not in software design.

Module approach is better because of separating things.

ajaxian: thats what I suspected but I need to know from usage.

Anyone that have used the feature in Yii?