Yes, but the adaptor requires an optical element to allow the lenses to focus to infinity (otherwise there will be a limit to how far away you can focus), which makes the adaptors expensive or quality degrading. The adaptors are fully manual as well, not AF and stop-down metering controlled with the aperture ring (the aperture you set is set all the time, not just when you take the shot).
However, other old lens mounts are much more suitable for adapting to EF, pentax K, olympus OM, contax/yashica, M42, leica R, and nikon F can all be adapted to canon with cheap no glass adaptors that don't have any impact on the quality (fully manual still though). If you're comfortable with manual focus and a stopped down viewfinder, there are some great bargains to be had.
