It depends on a number of factors; high ceilings can be a good thing if you are in a tracking room for drums, for example, and the room is not a square shape. Usually not what you want in a control room/mix environment though.
You should probably get a test mike and a software kit for checking the nodes and reflections in your room, but just guessing, without any data or dimensions or a recording/mixing sample or anything, I can tell you what's worked for me in a couple of different locations. One trick would be to put an acoustic "cloud" hanging over your mix position. That might help to kill reflections from the higher ceiling and also absorb some other frequencies too (if you use some of the rock wool, for instance). Another thing we did in one studio was to create a "faux drop ceiling," using material hung horizontally from wall to wall to lower the ceiling height. This will really only deal with the higher frequencies though, again, depending on what you use.
Another design you might look at emulating (depending quite a bit on your room dimensions, shape, layout, and ceiling height) would a more vintage control room concept called a "lede" ("live end, dead end"). It creates what it sounds like-- using room treatment, there is a live end of your room and a more dead one.
See here (
Early Sound Scattering & Control Room Design ) and also Google "lede room."
Hope that helps...
GJ