Scoliosis can lead to imbalances in your physique, especially in the shoulders. Most people have a natural tendancy to favor one side over the other and in folks with pronounces scoliosis this imbalance can become pretty pronounced. Aside from the standard treatments for scoliosis, you might want to emphasis unilateral excercises and work the lagging side a little harder than your 'strong side.' Like when doing overhead presses, do them with dumbells instead of a barbell and maybe try to squeeze out an extra rep or two on the weaker side.
I have a very mild case of scoliosis and one shoulder was noticably higher and larger than the other before I strated training. Over the years, good posture and solid training have pretty much eavened things out. Also, while symetry is important, the two sides of your body are not, and never will be identical to each other so to create the illusion of symetry you might have play around with different routines, assuming that's even important to you.