This might help someone:

The version of DOSBox TH is currently shipping with (0.74) gave me really really slow performance. I checked the DOSBox website and sure enough, Theme Hospital was listed as a regression for version 0.74. If you download DOSBox, 0.73 and manually replace the executable in the DOSBox folder, it fixes all the slowdown in full screen (or at least it did for me!)

I'll message this to Support, and you might consider doing the same.

Switched graphics settings to OpenGL for my wife and it seems to be working much better.
But will be looking at downgrading DosBOX if that does improve performance, too...

Switching to OpenGL worked for me too, in Windows 7, thanks! Windowed didn't do anything, didn't try downgrading dosbox. Apart from that, sound wise, I I replaced the ini with the file mentioned in the thread called "Changing the sound?" to get much better sound quality.*
Maybe GOG should make these settings default, or at least sticky a thread with both of these pieces of information?

* I would've posted a link, but I can't. Guess it's a new user thing.

Tried all of these and nothing worked, except increasing the cycle count to a ridiculous number, which still resulted in jittery scrolling and horrible sound.

I've been trying to get this game to run on this laptop in one form or another for a long time, and when I saw it was on sale here I thought my dreams had come true.

Nope.

I really hope this gets fixed :(

the game literally stops.. :( anyone able to fix this using a mac? thanks

I've noticed incredible slowdowns a couple of times after alt-tabbing out of the game. One time I managed to sort it somehow (don't recall what I did), but the other times I've quit and re-started the game, at which point everything runs smoothly again. When it has happened though, I can move the mouse and the pointer moves 5-10 seconds later. Such lag obviously makes it unplayable, but in my case at least it works to re-start the game.

Ah was just wondering what could be the problem. But then I stumbled upon your post, thanks! Cheers worked for me.

Just want to add something onto here - I got really fustrated with performance issues (it going redicuously slow when busier hospital)... tried all of the above with no success.

Then I changed the CPU cycles to "max" rather than "30000" and it fixed it 100% running as smooth as pie.

Hope this helps someone else in the future.