Sometimes mistaken for :
Common Comfrey (Symphytum officinale) but that has not got pure white flowers, but rather either yellowish-cream or dull purple flowers, much longer sepal teeth at least equal in length to the sepal tube and with the upper-stem leaves running down to the next leaf junction, and the stems are not nearly round but rather winged. It flowers a month later that White Comfrey.
Tuberous Comfrey (Symphytum tuberosum) but which has pale yellowish-cream flowers, pointed and very long sepal teeth, upper leaves which run a short way down the stem and which flowers up to two months later than White Comfrey.
Can be mistaken for : many other differing Comfreys, in particular those whose leaves never or only slightly run down the main stem:
But none of those Comfreys are pure white! They are all coloured, either red, blue, purple, yellow or off-white cream.
Russian Comfrey (Symphytum × uplandicum) but that has bright blue or purple flowers (and upper stem leaves that only slightly run down the stem)
Rough Comfrey (Symphytum asperum) but that has upper stem leaves which are shortly stalked (but still never running down the stem).
Creeping Comfrey (Symphytum grandiflorum) but that is shorter (20cm) and has flowers which are reddish-pink at first, turning yellowish-cream later and also much longer sepal teeth; and is also the first Comfrey to flower, flowering even before the already early White Comfrey.
Crimean Comfrey (Symphytum tauricum) but that has pale-yellow flowers (but still sometimes-stalked stem leaves which never run down the stem).
Some similarities to : the blue or purple flowered (other-times red) Lungworts such as Lungwort (Pulmonaria officinalis, which has spotted leaves), Narrow-Leaved Lungwort (Pulmonaria which has long and narrow leaves that are spotted)),
Mawson's Lungwort (Pulmonaria 'Mawson's Blue'', which has deep-blue flowers and narrow but un-spotted leaves,) and the very rare
Suffolk Lungwort (Pulmonaria obscura, which has broad and dark-green leaves with pink or purple flowers).
White Comfrey is a non-native plant used as a garden plant and which is well established in the wild, being found on hedge-banks and riversides.