Does crown moulding make a ceiling look higher or lower?

I personally don't think crown moulding does anything for the 'height' of a room, but it does really make it look nicer. And in general, any bright or lighter colors make a room look larger, whereas darker colors tend to shrink a rooms appearance.

Crown molding is a visual treat that adds a touch of elegance. Crown molding bridges the junction between walls and ceiling, a prominent location where the architectural accent can shine. In fact, using moldings that project further than the wall can provide an optical illusion that makes ceilings appear taller than they actually are. It also elevates a room's stature.

Some say crown molding and trim at the top of the walls should be painted in the same color as the walls so as not to draw attention upward, which would highlight the low ceiling height.

Crown moldings do not always have to be white. This is a frequent design faux pas; in fact, crown moldings should be the same color as the moldings that are already in your house. They can also be painted or stained to match existing color schemes, making them perfectly suitable for any room decor.

The size and height of the room you are working in should help determine the type or size of molding you install. If you have a large room with a higher ceiling (10 ft or more) the moldings can be larger and more complex without making the room look smaller or the moldings appearing too heavy. In a room with a shorter ceiling (less than 10 ft) a simpler, smaller crown molding will bring the viewer's eye up and make the ceiling feel higher.

I once read some where that moldings are the "jewelry" of the home. I agree.

Here's the thing about color and height...crown molding painted a light color ( or some shade of white) on walls painted light in color against a white ceiling will give you the most open feeling. If you accentuate the crown molding (light against dark or dark against light), it will only serve to box the room in. The later is often helpful in rooms that have very high ceilings and want a more intimate feel. Painting ceilings the same color as the walls (light or dark) will also create a boxy feeling. White ceilings will help to open up a room, regardless of the color on the wall or if you have crown molding. That said, mis-chosen paint colors are an easy fix! Dive in and have fun! Good luck.