Made mine slightly bigger.
But although the pill does do wonders for your skin (I'm on Mercilon, probably not quite as strong as Dianette as I only had mild acne) it's not worth going on the Pill just for that, unless you've exhausted other options such as Oxytetracline and you're really unhappy with your skin. I get so snappy and emotional around the time of my period it's unreal, but I guess I'd rather have that than my periods every two weeks (which is why I initially went on).
Definitely use it as a last resort though, unless you want it to prevent pregnancy/ regulate periods too.