Bathroom Remodeling Question

I just finished raising our bathroom ceiling back up to 8' using green board. My next step is to sheetrock the walls around the tub. I'm not sure if I should use cement board on the walls all the way up to the ceiling, or put cement board up to the point where the tile will stop and transition back to greenboard up to the ceiling sure if I want tile all the way up to the ceiling), or use greenboard for the entire wall. The existing wall had regular sheetrock behind the tile (from 1970's remodel) and the sheetrock was in very good condition. Which should I choose? Also, If I should be using cement board does that need to be taped at the seems?