Irish Cancer Society CEO Averil Power said people affected by cancer "need our support now more than ever" during the Covid-19 crisis.
Speaking on RTÉ's Today with Seán O'Rourke, Ms Power said it was important that people who were affected by cancer "know that we haven't forgotten them at this difficult time".
She has appealed to people for donations on today's "digital" Daffodil Day.
Ms Power said the Irish Cancer Society would normally raise €4m on an average Daffodil Day, which she said is a fifth of its annual funding.
She said the charity receives just 3% of its funding from the Government.
Ms Power said people who have cancer are some of those most vulnerable to the effects of Covid-19 and so "they need our support now more than ever".
She said night nurses and volunteer drivers, who take patients to and from their appointments, have received training in new protocols to be able to continue to carry out these services safely.
A new phone counselling service has also been implemented.
Ms Power said: "To help patients and those affected by cancer during this current crisis, which is all funded by donations.
"We only get 3% of our funding from the State so we have to fundraise €20m every year.
"A fifth of that comes in on Daffodil Day alone. Cancer patients are some of those most vulnerable to Covid-19 so we need to continue to provide vital services, like night nurses and volunteer drivers.
"We have also started new ones like phone counselling to help patients to cope during the current crisis, but all these services are funded by donations."
