There may be some situations wherein one would like to dispaly each CCK field in particular way.For example by default you have a lot of free space available in the right hand side of the node.One can theme CCK Fields so that it appears in free space.
How to do this?
To illustrate, let us assume that we have a content type named: blood_bank. The first job here is to create a template for theming this content type.By default node theming is done by node.tpl.php file. Copy this file, rename it to node-blood_bank.tpl.php file.Now the theming in blood_bank node will come from node-blood_bank.tpl.php file.Change this file according to your theming requirement. In this file you will see a variable called $content. This variable contains all information that is displayed in the node. You can remove this variable and output each filled in a way you want to see.