The Irish Cancer Society is calling on members of the public to get behind Daffodil Day today.
More than 5,000 volunteers are selling daffodils right across the country, and the charity said it was hoping to raise €3.4m. Last year's Daffodil Day was a wash-out due to torrential rain.
Some 30,000 people are diagnosed with the disease each year.
Head of fundraising with The Irish Cancer Society Mark Merritt said survival rates were improving all the time.
"(About 30,000) people will hear the words 'You've got cancer' this year, but the good news is that survival rates are increasing, for women by 20% and for men by 50%," he said.