Physical Size - The physical size of an LCD monitor is significantly smaller than that of a CRT monitor.  LCDs work off of a thin screen where as CRTs work off of tubes.  The thin size of the LCD allows you to free up valuable desktop space and put it places that a CRT would not fit.

Display Size - Advancements in LCD technology have made it possible for flat screen monitors to be as big or bigger than their CRT counterparts.  A 17" LCD monitor will measure 17" diagonally, where as a 17" CRT will most likely measure 16" or so diagonally.

Colors - Both CRT and LCD monitors are capable of displaying unlimited colors.  However the way in which the LCD monitors creates the color is easier on the eyes than the typical CRT monitors.

Power Consumption - LCD monitors consume significantly less power than CRTs.  This makes them perfect for laptop computers, allowing you to get the most use out of your battery.

Radiation - LCD monitors do not emit any harmful radiation, where as CRT monitors have been known to do so.

Price - Although the price of an LCD monitor is more than a CRT, the price has been coming down quite a bit over the past few years.  You should also consider the long term, not just the short term.  A CRT monitor will cost less in the short run, but will consume more power.  An LCD will cost more up front but will consume less power.  This might not seem like a problem for the average individual user, but if you run a company with 50 computers it becomes more of an issue.