Cats and lilies don't mix! Lillium species ("true lilies") such as Easter, Tiger, Asiatic, Oriental, etc., and daylilies (Hemerocallis) are highly toxic to cats, but not dogs or people.
Ingesting petals, leaves, the pollen, or just water from the vase can result in kidney failure and death. If your cat eats any part of a lily, seek veterinary attention immediately. Early treatment is imperative!
Safer cut flower choices include: Roses, sunflowers, tulips, irises, carnations, mums, baby's breath, hyacinth, and daffodils. These flowers can cause vomiting and diarrhea, but are not life threatening.