Thickness of the media. Type I is a little thinner. Type II sort of eclipsed Type I in capacity, but lately Type I has made a come back and has higher capacities too. For all practical purposes, just buy the capacity and brand name you are comfortable with. Occasionally, still digital cameras have had issues with certain brands and dpreview forum users would compile lists of which cards work with which cameras. I don't know if that's an issue with camcorders. Is the movie going on compact flash, or just still images? My Canon S1 IS still camera takes up to 1GB AVI movies, full size. The files are accepted by iMovie. Shirley On Mar 10, 2006, at 5:49 PM, Raymond Rogoway wrote: > What's the difference between a type I and a type II compactflash > memory card. My Camcorder can take both. Is it transfer speed?