Even though the EOS 20D digital SLR is also fully compatible with all Canon EF lenses, you have to remember it uses an APC-S Sensor which has 1.6 multifier.
35mm - 80mm equals to 56mm - 128mm, so you'll need a lens that would do 18mm and lower. 18 x 1.6 = 28.8mm
Here's a quote from Canon:
Here are some Canon EF-S lens offerings EF-S 10-22mm f/3.5-4.5 USM and EF-S 17-85mm f/4-5.6 IS USM zoom lenses as well as standard and USM versions of the EF-S 18-55mm f/3.5-5.6 zoom lens. The standard EF-S 18-55mm f/3.5-5.6 and more.