The number of people who are homeless and use drugs has almost doubled in the past six years.
The figures, released by the Health Research Board, have been described as "deeply concerning".
They show that the number of homeless people being treated for drug use has jumped from 5.1% in 2010 to 9.6% in 2016.
Tony Geoghegan from Merchants Quay Ireland believes the true number is probably higher.
Mr Geoghegan said: “We are deeply concerned to see that the number of people treated for problematic drug use who are homeless has almost doubled in the space of seven years, increasing from 453 people in 2010 up to 886 people in 2016.
"Homeless people find it very difficult by dint of their situation to enter drug treatment, so it is masking an even greater number of people there.
"Also there are people unfortunately who end up sleeping on the streets and in crisis hostels and so on."