Green board. Is it really horrible.
 

Im trying to figure out what to use in my bathroom on areas that will not be covered by tile, but will be in my shower at the top. If i use cement board it will look course, if i use drywall it will get wet, and mold etc. And every contractor in forums say never to use green board. but it seems like my bests option .any suggestions.

How much above the shower will be open ? Are you tiling the shower ? Or is it a fiberglass unit of some kind ? Why not just tile over the top of the shower ? It won't be that much tile.

Green board is fine use a good bathroom paint

About 20 inches will be open at the top. It is a tub surround at the bottom. and it has a tile pattern, therefore it would look awkward to put a different pattern tile at the top.

Cement board vs. greenboard
 

Hi. Last year, I replaced my bathroom walls and ceiling, because of moisture damage to the Greenboard that was installed professionally 6 years earlier. I also replaced the walls in the laundry area because the washer overflowed and flooded the floor destroying the Greenboard walls.

I was concerned about the same things you are--mold, mildew, and mostly the possibility of moisture/water getting through to the walls (drywall). BTW: I did it MYSELF--all of it (even installed a bathroom fan/light/heater in the ceiling, and replaced the cast iron fittings with abs plastic at the washer). No, I'm not an expert or professional--except when it comes to my house.

I won't go thru all the steps I did in removing the tub surround and tiling the tub/shower, because you have a specific question regarding wall choice. So...

In the bathroom: for the walls and under the tile, I used Custom Building Products WONDER BOARD 5'x3' x 1/2" Backer Board, (purchased at Home Depot). WONDER BOARD has a SMOOTH finish. (HARDIEBACKER cement board does not have a smooth finish.)

For the laundry area: for the walls I used WONDER BOARD and DUROCK Brand 5'x3' Cement Underlayment and DUROCK Brand 5'x3' Cement Board [purchased@Lowes]. I used all 3 types because it was what was in the garage and I find there is no difference.

To attach the cement board to the studs, I used a drywall bit and 1 1/4" coarse drywall screws.

For the wall seams and to cover the screws:
in the bathroom, I used thinset;
in the laundry area I used drywall tape and joint compound.

Where the walls meet the ceiling:
in the bathroom and laundry areas, I used 100% silicone paintable caulking--it's a great trick as opposed to using drywall tape and joint compond or paper-faced metal corner bead and joint compound.

After going over the joint compound 3 times (smoothing/sanding with a screen and spreading/fanning), I painted 2 coats of KILZ primer and then 2 coats of 2 coats BEHR interior/exterior high-gloss paint.

The walls and ceiling are smooth, water proof and look great.
Hope this helps. Good luck on your project.

P.S. I have not heard anything bad about Greenboard but, from personal experience, I prefer the WONDER BOARD for moisture/water applications.

I've used Greenboard in a number of my bathrooms and never had experienced any problems. This said, I kept them away from the shower and tub area. I've always used WonderBoard around the shower/tub areas and tiled around the shower/tub.

As malibubarbi says Wonder Board has a coarse and smooth side and you can install it either side out, depending upon how you plan on finishing the wall. I would go with that approach based upon your concerns.

If you use wonderboard or ? you will fill it with drywall filler that still needs to be protected with sealer and paint. Reg drywall was good for fifty years when painted properly. Green board is a step up and If you use good paint??

Drywall
 

In my area it's code to only use paperless drywall in a bathroom. (in an untiled area) Without the paper there's nothing for the mold to eat.