Check the packing that the battery pack comes in. The outer transparent plastic packaging and the cardboard backing should be glued together and not simply slide apart. Also check the unique hologram on the packaging. It should show the word 'Canon' running in horizontal bands. In Between these bands you will also see a helix that is overprinted with the word 'Genuine.' As a further check, when tilted from a front-on to a horizontal position, the hologram’s colour changes from gold to a greenish tint. If you do not see this change in color, the hologram is a fake.