Depends on the type. Some you only remove any dead or dying leaves whenever you see them (H. niger, sternii, ericsmithii, foetidus, argustifolius). Others like H orientalis hybrids I remove the leaves about now so that I can see the flowers as they open. However there is a school of thought which says one only needs to remove them if they are damaged. So please thissen really.
There is a thing called Hellebore Black Death which starts in the old leaves and you definitely should remove any which have black marks on them.

I agree Owd, it isnt a necessity to remove them, its just allows you to see the flowers more clearly. I only remove dead or badly damaged ones.

Great I do usually remove now to see the flowers but I have been questioned as if I was incorrect in doing it.Thanks

Well I have been removing them for the last 18 years here and we have one or two. They seem to thrive on it.

I have many in the garden and I have been removing the unslightly leaves for a few weeks now and as the flowers grow so to see them better.

Carol Klein of Glebe Cottage and Gardener's World cuts hers off to help the flowers be seen. I decided I liked mine the way they were and that the flowers didn't need my help. I only remove the untidy ones.

Me too, Linda. Some of the leaves are beautifully marbled. :-)

If the leaves are marbled then they are not the kind of Hellebore where the leaves can be removed. As I said in my first answer, it is only the H. orientalis hybrids which are treated like this.

You're right! I didn't read it carefully enough. Sorry.

I don't remove mine at all and I have many Hellebore O. hybrids, I feel it best to let nature do it's thing and let the plants photosynthesis naturally (with leaves on), I'm convinced this makes stronger plants.

Fair enough, I just hope you stay free of the dreaded Black Death of Hellebores.

Me too Owd.b. :)

I would add that I only remove leaves from mature plants and not from babies.