Masking is unavailable on Sony Vegas Platinum.You can only mask on Sony Vegas Pro, making it one of Vegas Pro's primary feature that attracts people to it. Platinum and Movie Studio are geared toward "hobby" video editors. Sony Vegas Pro is geared more towards semi-pro to professional video editors.I, personally, use Vegas Pro. I am not a professional video creator, I simply make video tutorials. So its fine to use it if you are an amateur or whatever.Apart from masking, the only difference between Vegas Pro, and Vegas Platinum, is that Vegas Pro has video scopes, unlimited tracks, more audio and HD capabilities, and a few more additional plug ins.So to answer your question, you cannot mask in Sony Vegas Platinum 9. You need Vegas Pro to do it.More on Sony Vegas Pro here:http://www.sonycreativesoftware.com/vegasproIt sells for around $550, in case your wondering.Hope that helps!-Techtopia