I recently upgraded from Leopard to Snow Leopard and I noticed that I have more capacity available on the Macintosh HD. I checked my files and applications and they are still on my computer. Can capacity on the HD change after an OS upgrade?

I recently upgraded from Leopard to Snow Leopard on my MacBook and I noticed that I have more capacity on the Macintosh HD than before the upgrade. I checked my files and applications and they are still on my computer and nothing appears to be missing. Before the upgrade I had around 111 GB capacity with around 10.50 GB available on the Mac HD but now after the upgrade I have 119 GB capacity and 20.92 GB available. Can capacity on the HD change after an OS upgrade?