YASHICA lens in canon bodies?

How well do old YASHICA lens mount in canon eos? Is it easily adaptable?

Yes, assuming you mean the contax/yashica mount. Yashica AF mount was different and I'm not sure if that can be adapted.

See here as referenced in the EF Lens FAQ Sticky at the top of this forum.

The sticky doesn't mention Yashica AF mount, so I've been doing a little internet research. I still haven't found out for sure what the registration distance on the mount is, but it seems very much like the Minolta AF mount in other regards, so it might be 44.5mm, like the Minolta. In any case there do not seem to be any adaptors (they'd have to be 0.5mm thick if my above supposition is correct), but regardless of any registration length restrictions you wouldn't really be able to use Yashica AF lenses as they, like EOS, use electronic aperture control. As that wouldn't work through an adaptor, and the lens has no aperture ring, you wouldn't be able to control the lens at all.

All of that applies only to Yashica AF, which is not the same as Contax/Yashica. C/Y works fine with a cheap adaptor.

Thanks for the info.