Can i use old canon lenses on new digital cameras?
Depends how old. All autofocus Canon lenses should work as Canon redesigned the whol elens mount for autofocus. So autofocus lenses from film Canons will work on the digital models. Older manual focus Canons generally will not work. There may be aftermarket adaptors but some functionality is lost.
Depends on how old the lenses are. Canon wanted to make it easy for people who want a better camera without the worries of spending hundreds of dollars on new lenses. So it depends on the lenses series and the camera series. Exp: the EF lenses can fit the EOS digital SLR series. Canon also carries a wide variety of lens adapters. So contacting canon directly or visit a professional camera store.